Libby-175
-Epistolary
-Jump pack
-Rage
-Sword
He's fine, but just curious - who is he running with?
Sanguinary guard- 290
-Death mask x2
-Banner
-Infernus pistol
"Entire squad can be given death masks for ..." - think paying the price once is enough get 5 masks. And lack of PF may end bad here if enemy dreadnought is agile and cunning (if Libby doesn't fly with them). And I'd also suggest having Priest here - it'd be sad to lose these golden (both literally and in price) guys for small arms fire.
Assault squad-205
-Flamer
-Meltagun
Assault squad-190
-Flamer
Personally I don't like assault squads without special CC weapons. Sarge's attacks aren't used fully without it. And I'd put both flamers in a single squad.
Death company-135
-Jump pack
-Thunder hammer
After these guys catch a copule of missiles (nothing more to shoot at with ML in your army) hammer-wielder will die in CC with almost no chance to strike even once.
DC would work as a fire magnet but won't pose much threat after the first round of enemy shooting.
Sanguinary Priest - maybe the biggest force multiplier in BA codex - is not used in your list.
Drop DC, get a priest with PW, give PW to sarges, buy another melta (making 2melta/2flamers or 2 versatile squads) and maybe second infernus to SG after you recalculate their cost.
Or maybe even get 2 priests - you may really need 2 bubbles with 20+models on the table. But with FC and FNP on all models your army will get from considerable to scary at once.
Hope this helps.