Analyze what bots / FF brings:
A lot of DEF to cover you and them.
Ranged attacks primarily.
Knockback from bot blasts.
So I think if you have some group stealth that would be nice and allow your bot pack to get into range without being seen: dark, storm, cold have such auras.
You'll need to be able to heal yourself and the MM/bots at range. You'll want an aura heal over a ST to catch everyone at once. There are several options here: rad, dark, emp, time, nature, thermal, etc... you won't get it from storm, traps, kin, poison, cold, sonic, etc.
Some resistance to add to the mix would be nice. So the stealth auras mentioned above would work, along with sonic.
The kb will knock things out of patches and anchor auras, so you'll need to be selective on where you place those if you take a set with them... I can't think of a defender primary that roots targets to prevent it.
For me, putting that all together, I'd think something dark/ would be really good. It also has -RES / slow patch, fear, hold, rez, -To Hit... would be a great collection of debuffs and controls to go along with your partner's damage and ranged blasting potential. Also, shadowfall will plug FF's psi hole somewhat.
I also like rad/ and time/... no stealth aura, but checks a lot of the other boxes and brings some strong debuffs / buffs to the party.