You do realize the comic was focusing on Jango himself, right? They can't show all 300 Mandalorians, because the comic was about JANGO FETT. And again, canonically, Komari Vosa, who was at that battlefield, killed at least 20 Mandalorians that day, as she states in the Bounty Hunter game. And that game is.......drum roll please......CANON! THAT GAME IS CANON TO LEGENDS AS A C-CANON WORK! The game shows us the resolution regarding the rivalry between Jango Fett and Montross, how Jango was chosen as the clone template, and how he met Zam Wessel and partnered up with her. Again, this goes to show your utter stupidity as a debater. You can't pull in C-canon works like the Traviss books and the early Marvel Star Wars comics starring Fenn Shysa and say that other C-canon works aren't canon. I'm not the biggest fan of LOTF and the Traviss books, but that shit is canon to Legends and a part of C-canon, and I can't get around that as much as I'd love to.
Finis Valorum noted how the Jedi are too few to protect the galaxy. Hence why he wasn't thrilled with the prospect of having them as a defense force, and why the Senate and the Jedi Order were hesitant to fight the Separatists until they discovered that a clone army trained and indoctrinated by Mandalorians just happened to be around, ready to kill and die for the Republic. That doesn't mean Jedi can't do military things, since for 25,000 YEARS, THEY'VE BEEN FIGHTING WARS ON BEHALF OF THE REPUBLIC! And no, before you pull out the whole "Lucas didn't believe in the Jedi vs. Sith Wars!" even TCW has Sidious talk about past Sith Empires during the Slaves of the Republic arc when he says that past Sith Empires were built on the backs of slaves AND it also has Darth Bane, a Sith who survived the last Sith vs. Jedi war before the Clone Wars, meaning that Sith Empires did exist in the past AND the Jedi put the kibosh on them, even in TCW which had input from Lucas. Other media that had input from Lucas includes Force Unleashed, where in the Wii/PS2 version, Darth Desolous and Darth Phobos existed as simulacrums-Darth Desolus killed a thousand Jedi, and Darth Phobos was such a threat that Jedi and Sith allied with each other to put her down, meaning that the Jedi vs. Sith Wars obviously existed.
And of course, there are non-Sith wars like the Mandalorian Wars and the Pius Dea Crusades where the Jedi played a part, not to mention that during the 1000-year peace after the last Sith War and before the Clone Wars, the Jedi fought summer wars all the time to ensure that the Republic remains afloat and stable. Down to the point where Republic Judicial Terrinald Screed identifies the Jedi as "the august order that has staved off warfare for a millennium." How did they do that? By fighting summer wars and keeping threats minimal before they exploded into full-scale war. The only reason they allowed the Separatists to build up is because they thought the Seps and Count Dooku were just political activists. If they had known that Dooku was planning military action from the start, they'd have taken his head before his Separatist movement grew into a threat. When he was making an argument for a unified Republic army and navy, Screed also talks about how the Jedi used to lead armies to victories in the past, and he argued that the Jedi could lead an army to victory in the future:
"Relying on Planetary Security or Sector Forces is a stop-gap solution, as the inefficiencies of the Stark Hyperspace War so painfully demonstrated. The solution is obvious -- a unified military coordinated from Coruscant. Our ancient history has proven this has time and again -- the Great Sith War, the Kanz Disorders, the Virujansi Uprising -- times when a unified Republic Navy and Army were strong. And now, as then, there is still a role for the Jedi in today's galaxy: leading an army to victory."
-Republic Judicial Terrinald Screed, arguing for a unified Republic Army and Navy, Holonet News Point/Counterpoint on the Military Creation Act
So yeah, that whole "Jedi should be kept away from the military" thing makes no sense, since in the past, the Jedi were leading armies to victory, and in the Original Trilogy, Princess Leia Organa identifies Obi-Wan Kenobi as GENERAL Kenobi, and she wants his aid for the Rebellion. Meaning that had he survived the mission to rescue Leia from the Death Star, he'd be a general in the Rebel Alliance movement, or perhaps even the LEADER of the Alliance military, almost akin to a shogun for Leia and Mon Mothma. (Now I have an image in my head of Alec Guiness wearing Samurai armor. And it's awesome!)
KOTOR was only following Tales of the Jedi's depiction of the Mandalorians, which didn't go with loose clan structures but rather had them be a large, nomadic military force under an autocrat, a force that valued war and were itching for a new crusade to break out. They even stated in the Tales of the Jedi comics that the Mandalorians are "ruthless and implacable" and they "live for the savagery of a mercenary attack." Meaning that they were savage and bloodthirsty at war. Even in the KOTOR comics, which somewhat recognized Traviss' language and works, they still had the Mandalorians organizing under an army under Cassus Fett, AKA the guy who taught the Mandalorians about logistics. You know, that one thing in war YOU ABSOLUTELY CAN'T FUCK UP? Mandalore the Ultimate even described it as "that basic word Cassus Fett uses" and he used that along with legends such as the legend of "Rohlan the questioner" to organize the Mandalorians into a unified army. So basically, they were already ditching the clan-based stuff for a unified army and navy where the Mandalorians acted as a unified force. 4000 years before the rise of the Empire. After they lost the Mandalorian Wars, Canderous rebuilt the Mandalorians on Mandalore the Ultimate's model.
As for TOR, the Mandalorians were scattered mercenaries and individuals who didn't even have a Mandalore until Imperial Intelligence played them like a fiddle and propped up a fake Mandalore via rigging gladiatorial matches. The guy who replaced said Mandalore continued the tradition and had the Mandalorians remain as a centralized army under his watch. In the New Sith Wars, at most, we got a mention of the Mandalorians being bought off by the Jedi to attack the Sith.
And of course, the other Clone Wars books barely mentioned Mandalorian involvement on behalf of Mandalore the Resurrector, some even had Boba Fett openly milling around, meeting guys like Anakin, and TCW had Boba Fett openly bounty-hunting AND the Death Watch/Pacifists ruling Mandalore.
NONE of these works had Traviss' version of the Mandalorians where they were a loose collection of clans that did whatever they did while someone who bore the title of Mandalore was around. Sure, Mandalorian clans existed, but they existed to serve Mandalore. At most, MAYBE you can argue that prior to Imperial Inteilligence creating their fake Mandalore, the clans may have been going off doing their own thing, but the lore videos for that talks about Mandalorian mercenaries as individuals and don't even mention clans. In those lore videos, there were Mandalorian mercenaries and bounty hunters who fought in gladiatorial arenas for blood, glory, and money-something Traviss doesn't have in her version of the Mandalorians. In KOTOR and Tales of the Jedi, they were an autocracy under one ruler who went on crusades. In TOR, they were individual mercenaries and bounty hunters who fought in gladiator matches for fame and glory until Imperial Intelligence manipulated them into rallying under a Mandalorian whom they propped up as Mandalore, and they went back to being an autocracy under a ruler. In TCW, they were split between a peaceful nation under one ruler, and a warlike force under one ruler, and even when Darth Maul sauntered in, no talk of appeasing or working with different clans came in, he just took control of Death Watch and became an absolute monarch, like Pre Vizsla and Duchess Satine before him. Even in Rebels, they acknowledge this when Sabine and Maul exchange eye contact and Maul recognizes his former subjects.
Maul: "A Mandalorian? You of all should trust me. For did I not once rule your people?"
Zeb: "Is that true?"
Sabine: "Unfortunately."
And of course, Mandalorians killing Jedi is rather rare in many of these works. At most, in TOR, they won ONE space battle against Jedi who were exhausted facing Sith 24/7, but they got their cans kicked by Republic grunts and smugglers, and in the main game, Mandalorian leaders like Ironfist and their forces get their cans kicked by Jedi, up-jumped Republic grunts, and smugglers with cheeky attitudes. In TOR's story mode they accomplished nothing, and the empire that paid them to help win the war was collapsing by the end of it. In Tales of the Jedi, they lost the war despite being backed up by Krath and Dark Jedi, and in the Mandalorian Wars, they only got far because the Jedi had cold feet getting into it, had the Jedi Council acted sooner, the war would have ended faster. In the KOTOR game proper, they were bandits who preyed on the weak and got their cans kicked by a Jedi player, and in KOTOR 2, the Jedi Revan had to install a new Mandalore to get the Mandalorians to rebuild and move away from mercenary work and banditry. In the New Sith Wars they had Jedi support. In Galidraan, 300 Mandalorians were exterminated by a couple dozen Jedi, and in TCW, even padawans like Ahsoka Tano kill/defeat Mandalorians rather easily. Even Kenobi, who was captured earlier by Mandalorians in an ambush, managed to hold off Mandalorian warriors with a blaster, which isn't his preferred weapon of choice. In the Original Trilogy Era, they were enslaved by the Empire and had to defeat the local Imperial garrison with ambushes and hit-and-run attacks, and in the Legacy Era, they were sent packing by Stormtroopers.
NONE of these eras had the Mandalorians defeat the Jedi in droves. At most, they caused some Jedi casualties in Galidraan and the Mandalorian Wars, and they defeated the Jedi ONCE in TOR, but in every other war against the Jedi, they lose in droves. Even in the Mandalorian Wars, they fought against a rogue sect of the Jedi Order which only had some support from the Jedi Council, and they lost so horribly that their chances of being a galactic superpower was lost. Forever.
Hence why I actually admired Canderous, because he's like Revan's version of General Grievous-he guts Sith for a living under Revan's command. But that makes him a rarity. Same with Jango Fett, Akaavi Spar, Sherruk, and a precious few other Mandalorians who have killed Jedi-they're not in the majority. Otherwise, in times like the Mandalorian Wars, you'd see even common soldiers kill Jedi and collect lightsabers like Sherruk and Grievous do. Instead, it's usually leaders like Canderous and Jango who kill Jedi, while the rest of the Mandos get slaughtered by the bucketloads like the Mandalorians at Galidraan by the Jedi.