I assume you are taking six units of 20 boyz each? Just want to make sure.
Deff Rolla on each would be nice.
Removing 30 boyz with rokkits and 'ard boyz could go to adding more weapons to the BWs since you don't want them to immobilize.
IMO, 3 full squadrons of rokkit buggies would do better than 3 squads of 2 Deffkoptas. If 1 deffkopta dies, you are forced into a Morale Save for the other, which has a decent chance to run off the board.
You could also add a burna unit to throw into a BW versus other horde armies. Could prove much fun.
Lootas aren't bad either, and may prove more effective than Snikrot led kommandos in the long run.
What to do with the rest of the points relies on you (and others to critique

).