Riddle me this brothers of the imperium? When running an 1850 game and you have your tempestus at 800 pts what do you use for an ally? May I suggest a more up close and personal as well as defensive on the advance option to my previous suggestions. Speaking of the Black Templars.
So here's the idea. You have a land raider spearhead for near unkillable land raider and inside are 2 squads of centurians along with Grimaldi's with a crusadersquad and his cenobites. Drop podding in is an ironclad dreadnaught to have him and the centurians form another formation. The land raiders provide a wall for your primes (if you prefer to use them) to start out behind (which immune to all but explodes results) and as the land raiders flatout ot tank shock forward they get the assault centurians to the fight. Also don't forget about the threat of the ironclad drop pod on turn one as well.
So what to you think? Is this a good ally for the militarum's best? Should it be all tempeatus with tactical shooting and grab shute insertions? I hope this helps with all of your curiosities of a very obscure but versital Dex.