Killswitch- The random dozers are actually fairly important. In a lot of my games I could fit most of my transports without being in terrain, however 1 or 2 would have to be in it, thus having those 2 tanks with dozers actually allows me to effecitively ignore that little hastle.
The strike squads make this list. The power of this list comes from it's redundancy of units capable of fighting in close combat, and from its fire power. I've tried henchmen instead of 2 of the strike squads, I either lose combat power or fire power. This army thrives on its duality, taking specialized squads goes agaisnt that. Purifiers should not be in razorbacks, believe me. I've trued it and it's just more effective to shoot out the hatch with psy cannons.
Black Blow Fly- I've also tried 10 man purifiers. I like keeping them in rhinos and giving them 2 psy cannons (to shoot out the hatch) and 2 incineraters for when the going gets tough.
One thing I'm considering is dropping the dozers and coteaz to get 2 ordo xenos inquistors with rad and psychotrok greandes. That way I can give 2 units ld 10 stubborn, and have some nasty grenades to push me over the edge in combat. I just miss the re roll to seize, the hammer, and sactuary.