Personally I find Drazhar expensive for what he does but by all means go for it. You can save pts from the Kalvex and onslaught since if memory serves Drazhar comes with the Ability and with the demi klaives.
If I was you I would group the wyches in groups of 10 saving the points from the 2 extra raiders to get a ravager. I find your army a bit weak in the Anti-tank department and a ravager would go a long.
Consider replacing one Talos for a Cronos equipped with a spirit probe. The 2 pain tokens per turn in can provide to any friendly unit within 12" more then makes up for its lack of WS and Str compared to the Talos.
Other then that the list is looking good.