What's the point in two detachments? It all fits in one.
If you want a lascannon platform a predator (auto/las or tri-las) would do more for you than a helbrute. You could use that as your objective grabber and lose one or both units of cultists since they're not needed for minimum troop requirements
What's the idea with the terminators? Deepstrike? I wouldn't bother with the reaper autocannon, I'd spend those points on a heavy flamer and power fist, then drop one of the combi weapons and add another fist