Consider creating a 'hive-mind' pet that can control other pets in a group. One player in a raid can then control all the pets as a group (or at least all the pets of players that release control of their pets).

Maybe make a specific new pet type (hellbug? a mechanical?) that goes into the 'netowork' for the encounter, but that would probably require figuring out how to fit that pet type into different classes in raid-worthy soul trees. Shouldn't be too hard if, using hellbugs as an example, Rangers, Beastmasters, Druids, and Pyros all had hellbug versions of existing pets. Could also be a Patron ability or a purchaseable pet skin that enabled the networking using existing pet types.

Might add new/enhanced abilities for the pet-using souls for the networking, like enhancing Ranger's pet heal ability so it would spread from his pet to others networked to his.

Of course the hive-mind/network would likely require creating encounters that make use of such an ability (raid instances, zone events, raid rifts, PVP, hunt/nightmare rifts). Maybe add a hard-mode-like version of existing encounters that would require networked pets to get through it. I think this would be unique among MMOs - the one's I've played anyway.

Unless you share the idea and do some cross-over with the Defiance Devs...and either a hellbug hive pet or a mechanical one would fit both games.