I never really liked the Cryo Cannon for driller. My thinking was "I've frozen a bunch of enemies, but I can't actually kill them all quickly before they unfreeze, so what?" I often found myself running out of drill fuel trying to drill frozen glyphids. I've tried snowball, ice spear, tuned cooler, but never really enjoyed them. Instead I went for a more damage oriented build, it plays more like an angry Mel Gibson Santa, and less like friendly Tim Allen Santa who can freeze bugs but not actually kill them all.
Cryo Cannon
Overclock: Ice Storm
1-1-1-1-2
Base Ammo: 500
This plays more like a flamethrower, and even though the freezing power is very low I can still freeze a Bulk Detonator/Dreadnoughts on Haz 5 (have to aim at the ground a bit to get the extra freezing from the ground ice). You can pretty much shoot forever though. In practice it is much easier to get the vampire procs with this build because I can actually damage a frozen enemy down to low health with the Cryo Cannon, and just tap it once/twice with the drills if I need health. I don't need to switch to my secondary to do good damage either, because Ice Storm multiplies the damage a lot on frozen enemies. Regular grunts are vaporized in short order. The only con I've found is that I can't freeze as many mactera as easily, and usually kill them before freezing them (unless I'm close to them and the AOE freezing kicks in). If there are too many mactera, I will cook a HE Grenade, and throw it so it air bursts into the middle of the pack, it will take out a couple, and fear the rest, preventing them from shooting you to death. Alternatively drop a C4 (have to have AOE stun picked on it), Dash perk away, then trigger it to stun everything, and give more breathing room.
Wave cooker
Overclock: Mega Power Supply
2-3-1-1-2
Base Ammo: 500
Since the Ice Storm overclock incentivizes NOT switching to a secondary weapon on frozen bugs (it ramps up damage on frozen enemies), I speccd out the wave cooker WITHOUT Exothermic Reactor/Temperature amplifier, and instead went with Boiler Ray + slow, something I've never really used much. It's surprisingly good at deleting swarmers, and with the wide angle lens turned on you can delete the flying swarmers easily as well, this conserves our precious Cryo Cannon ammo for more important targets. The boiler ray explosion does good damage (100 explosion; 2.5m radius), and you can take out a good number of grouped up grunts from long distance if you get lucky procs of Boiler Ray (target the basic Glyphid grunt). With the Mega Power Supply overclock you can use your secondary liberally, and combined with HE grenades you can kill most larger swarms before they get into Cryo Cannon range (terrain permitting). You know Boiler Ray has proc'd, because little spikes shoot out of the enemy as it explodes, and this damages nearby enemies. This is more noticeable on a pack of swarmers, because you'll shoot one or two swarmers and then suddenly the whole group dies.
You can really rack up the kills, and if you get used to using your secondary weapon more like a primary weapon (+ cooked HE grenades), I don't find myself starving for ammunition. (If you haven't tried HE grenades since they added the ability to cook grenades DO IT! Very fun getting them to air burst on walls and ceilings) If you are flush with ammo you can just throw yourself into a swarm and kill everything with the Cryo Cannon, everything dies, Oppressors, Praetorians, doesn't matter. (don't forget to shoot the feet of the enemy).
So if you never really liked Cryo Cannon, give this a try. If you do, let me know what you think.
