Generally speaking, build the Deathwatch around Alpha strike is the way to go. It is noticed that they ARE Glass Cannons for their points and they have some really shining toys. Also, they have Detachment rules to allow everyone
DS so maybe you don't need that many Droppod it can save points and your money

Fighting WarConvocation, it is when you can consider using Null deployment and alpha strike them. What you need maybe is more equipments that reduce enemy cover saves. Auspex you might want to consider.
I suggest take a few Librarians in your kill teams. Fish for Perfect Timing to Ignore cover or Invisibility to give your important expensive guys the only chance of survival. Also, it helps you to deny those nasty Psychic power from those Nids-Human mutant abominations.
Fighting
GSC is totally another story. It is better to take lots of Rhinos not Droppods. They can easily
MSU which is what your expensive guys can never achieve. Never try to out melee them, their First Curse formation can dish out 100 S5 rending attacks plus 6 S7 AP3 rending attacks which by maths will take out IK and WK before their opponent strikes. They can redeploy easily and Concentrate on and eat your army part by part. If you deep strike, droppod or not, your guys are footsloging and been very slow and out of protection, so are basically waiting to be wiped. Rhinos on the other hand, a 35pts transport give your expensive guys good protection against first wave of combat, and allow you to shoot out, as well as you can bubble warp.