What's the point in two detachments? It all fits in one.
Ah, that would be my apparent misunderstanding of force org.
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
Helbrute is in there because i already have the model. I hadn't really looked into taking any tanks, do you think the shooty platform is well taken care of by the trio of oblits? If so, then i could probably change the helbrute's role entirely.
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
Ya, terminators would be a deep striking unit to harass. Basically a similar role as the raptors but less mobile (so DS instead).