I disagree, I think the design worked, but there would need to be some adjustments to the cabal function in the current environment.
The idea of there being member limits is a good one. (5 mages/5 melee/ 5 priest)

Some other ideas:
Nexus is strictly limited in what they do to correct imbalance. Retrieve cabal items, and hunt alone those who hold power in the balance. Except villagers, they are always fair game, that's just fun for everyone on both sides.

No bandwagoning with those of the less in power cabal. Nexus members can only trust cabal members, none others. (to address the 2 imp +5 nexus death squad and though I think it is bull, the betrayal arguments people love to make)

There would need to be a shift in how retrievals work though, where Nexus raiding the empire outer sends back the Orb, but only when darkness tips. So they can only retrieve items of those out of power, and only on their own.

Nexus has limited abilities to hold cabal items. maybe a time limit or based on balance, though returning items could probably cause a shift.

Nexus does tend to cause an over correction to the underpowered side when the tipping is slight (if there is at least 2 nexus people on). When one side is overpowered, nexus is more of an evening out and functions as I believe is intended.

And remove the bond, but maybe beef up vanguard as more than just dam redux. Like it gives one other effect, maybe haste, controlled translucence. OR let them dump things into it to get added effects, but at a cost. Like if you want haste, max hp goes down 100 for the duration. IF you want stoneskin, it goes down 200 etc.

I don't know, smarter people than me could probably come up with a good system to make vanguard better in place of the bond.

I think Nexus is good, and somewhat necessary. Problem is it does tend to help evils more, cause evils will raid/hunt nexus, but goods usually won't.