I generally try to use anything that isn’t meta, and is really like weapons with a unique trait/gimmick. The Hystrix is a secondary I’ve been using a lot more because you can cycle through an element to force proc heat/cold/electric/toxin, which is really useful for different setups like heat if you want to use Cascadia Flare or cold if you’re trying to boost crit damage/slow demolysts without interfering with your modded elemental combos. It does have a fairly small magazine,so it can be harder to use without some form of ammo efficiency/infinite ammo.
The problem with support Wisp/support frames in general is that if you’re already going into endgame content, you can usually expect your team’s kits to already be sufficient for that content. You can increase their survivability further by making use of shock motes to stun enemies and rad procs but this typically just slows down missions (especially the shock motes in defense missions) if they’re used in situations where they aren’t really needed, and can cause issues with builds that make use of enemies clumping together like if you’re trying to make use of Gas/Blast or have a Harrow in the squad trying to buff with Covenant. Rad procs from breach surge usually aren’t as much of an issue though.
Breach Surge is a lot less useful now that enemies are often protected by overguard, ignoring the blind effect and being immune to the CC effects of Radiation procs, I think they might even be immune to friendly fire too (they aren’t targetted, and I think they’re immune enemy AOE attacks like a Bombard’s rockets). You can still try to make use of it though, there’s only so many enemies that can attack at the same time so you can still reduce the number of enemies attacking your team/the objective at the same time.
Pillage/Fire Walker for status cleanse; Pillage gives you Armor Strip at the same time while Fire Walker gives to a movement speed boost for memes. Your team still needs to walk through the flames though but it’s a more passive in its use versus Pillage which requires you to cast every time you want to use it. With Overguard being on everything now, status cleansing is a lot less useful, but it was still nice to have for Sorties.
I think you’re much better off modding to specialize for your loadout and letting your team pick up the buffs passively instead of trying to directly buff your team.