The combistick was never OP for the damage it deals, though it used to be more which made it objectively better (obviously). Why the stick is used by just about every Predator and why it’s so OP is the reach and cone of threat it offers. The Predator doesn’t have to get in too close or run after fireteam members when he can swing and hit them from a pretty far distance and at odd angles. The actual hitbox of the stick is further than the animation would suggest and this can really destroy newer players as they think they have more time to react than they actually do.
For example: A Berserker is chasing down a Scout with double time, anything other than the stick will see him having to run longer to close the distance before he can take a swing and probably score only one hit. This allows the FT to regroup and your easy kill is now safe as you’re getting shot. In that same situation, a stick would provide you with enough reach to strike at least twice before having to run again and more often than not, you will get the kill.
I’m also aware that a better strategy would be to net gun or range them down if they’re damaged but that’s not the point I’m making.