The Jetbikes are the easiest, at least as far as telling you how I would use them goes, they run out last minute and take the points that you have kept your opponent off of and contest the points that you haven't. They might also be useful for hit-and-run tactics.
Yes and at the same time no. The reason i don't gve them a cannon is because i need their twin linked shots to help force grounding tests from flying MC's. They also start the game in reserve so they do not get alpha'ed off the table. I also use them because if you destroy a section of the fortress it becomes imassible terrain. Jetbikes can fly on impassible terrain, meanig i can prevent them from being assualted and in some cases even shot at. They have a very high life expectincy.
Without going into the Tau units, that i use to fill in gaps, what can you do with your lists keeping in mind the above tactics. I see at least two things.
The Eldar, more than any other army, should not only look at the output of each unit individually, but the synergy of multiple units together and their role in the force as a whole. - Fable