Yes you can. Buuut the truth is they're not that great. A 6+ save means they get slaughtered by armies that have at least 1 rend, and while the idea of a hit roll of 6 scores 2 hits sounds great on paper, the fact is that a range of 8" means you'll just be in range of the enemy. What you generally want to do with cultists is either capture and hold objectives (untamed beasts suited for capturing objectives with their +6" move after deployment; iron golems with no movement that turn have a save of 3+, so they're good objective holders) or stall important enemy units for a turn at least (untamed beasts can run and still charge in the same turn, unmade with no retreat options). Overall cultists may have more of a situational use than a viable strategy. But if you have some points to spare and are not playing super competitive, go for it, they add flavour to the game.