The Best Setup that I have found for an Squad of Swooping Hawks it this:
4 Hawks
1 Exarch
Sunrifle, Sky Leap
Tactics Like This:
Start on the field in cover as far forward as possible.
1st turn:
Jump move into good firing position
you get 8 24" range S3 AP 5 shots and 6 S3 AP5 pinning shots
2nd turn
Sky Leap Out
3rd & subsequent
DS in and drop a large plate of death ANYWHERE ON THE FIELD. Sky Leap Out.
6th turn:
DS in and drop your large plate of death
claim a table quarter or objective.
Using this strategy, your hawks are almost impossible to shoot down (AA and inquisitors are all that can shoot them) and you will take out more than you think.
Throw in an autarch and get +1 to your reserve rolls to bring them back into play
Smile and watch your opponent hate them to almost no avail.