I don't think mixing a Kabal with Covens is ever a bad way to start. In recent times we got hit by the power creep, especially those of the Marines but all in all we are still viable.
Both, Venoms and Raiders are viable. Venoms are my to-go choice with Flayed Skull (for 19" move awesomeness), otherwise Raiders really aren't bad either. Also, Raiders can now transport multiple units so you can transport 2x 5 man squads of Warriors, Wyches or Wracks (interchangeably).
Depending on the enemy army, key transports getting blown up early is a problem, but I don't think its as bad is it was in previous editions. On top, we have stratagems that enhance our cover safe, make one unit -1 to hit or just cover greater distances. So that definitely helps.
You should definitely field some Taloi or Grotesques. And with the obsessions of the Prophets of Flesh you get a no-overwatch relic, a 4+ invul on all units and another D3 CP at the start of the game.