My plan to still get list is
1x Mephiston
1x Dante
1x Slam Captain
10x Sanguinary Guard
10x Death company
1x Death Company dreadnaught.
1x Techmarine( or primaris techmarine)
1x Devastator squad(maybe???)
1x BA Tactical Squad(maybe???)
???x Assault Intercessors
So I ask space marine fags, what should I add? Anything I shouldnt buy?
I've been putting together a BA army this year so I'll repeat some of the advice I've heard while doing research.
Firstly, definitely ditch the devastators and Tac squads. They're not worth the cost anymore and other units fill their role better. I would swap them for Intercessors, they look quite good in 9th and will hold up your backline while your Sang guard holds objectives (very durable compared to DC) and take on elites. Swap the DC dread for a Librarian dread. The DC dread is too slow and being melee only = it will get dumpstered long before it closes into melee. The good thing about Lib dreads is you can get that fucker into close combat very quickly via relic. If you want a shooty dread, Leviathan dreads with duel storm cannon arrays have been recommended, those will be pricey in 9th but with small boards they will be able to cover a lot. Also, consider an Invictor warsuit, the changes made them make them very appealing too.
The techmarine, I'm not sure how it will play out in 9th with the bigger focus on vehicles but generally they aren't very efficient to bring along either, especially since your list isn't vehicle heavy. I'm not really sure Assault Intercessors will mesh well into a BA army either given they can't take jumppacks, and BA is all about the jumpies. They will be a bit slow, the point space would be better applied to more DC or Sang. Since you are running DC, I would also look into getting Lemartes as he can buff them. You might also look into the Sanguinor to buff the SGs.
As i've had it explained to me, you want a lot of DC against horde armies (they have a lot of hits and rerolls), a lot of SG for elite-type armies. In high point games where you can bring both, use DC to hit the enemy early and make them deal with them along with the Lib dread, then move SG up to take out the biggest threats while everyone else secures objectives. DC is the hammer to smash the enemy initially, SG is the dagger that makes the lethal cuts.
For 9th ed it's looking like a mix of melee and shootie is going to be a strong composition. But until a lot of 9th edition games are played and the rules are more fleshed out it's a bit speculative.
Edit: One more thing, Mephiston got hit with a pretty big point increase so it's looking like swapping in the Lib Dread for him (you generally want one or the other) is going to be the way we go. Unfortunate, he's a cool ass character.