You want nest as fast as possible. He pretty much has one use currently at top end arena matches, go first vs palp/treya teams, apply aoe to stop nihilis and the team from gaining turn meter, knock 20% off and allow the rest of your squad to go first. Potency matters as you don’t want it to be resisted.
After that nest has a Stun, chances are by the third turn the fight has been decisively decided and his use will be minimal at best.
If you have top end competive mods on your shard your nest will be faster than any thrawn, and if your using sith you should be able to be faster than any Vader when a match starts. Mine personally runs at 294 speed.
Speed>>>>>>potency>health (more health will help him not be one shot after his turn), protection is irrelevant.
I say all this having sat in 1-5 on my shard and facing pretty much every possible meta team at the top end with barely anyone able to beat me and almost everyone avoiding me.