Alkamoshater vitality build does 4:39, maybe not a monster score like yours but not as if it can’t survive a lost souls nerf. Also this is sort of a moot point since if you nerf the skeletons special attacks you will also be nerfing the vitality builds in the proces, as well as the aether skeleton builds and the fire defilers. If you lower the flats on the rings they lose value with pet builds that don’t have the luxury of so many pets.
In my opinion the issue is definitely the set, the set basically combines duplication of the strongest allround pet in the game with buffs to the highest damage pet skill in the game. A toxic combination if you ask me, but if the skeleton bonuses are shifted more towards defense then I think it can be balanced. Also to equalize with vitality, the %vitality bonuses can be raised.
A pyromancer that just uses the 2 dogs and forfeits all the other bonuses can already walk around in SR80, unlike a skeleton defiler for example. My strongest hybrid pet build that can almost do SR85 happens to be based on ghol and doesn’t use any skeletons at all, so I’m pretty sure the duplication of the Blightfiend has something to do with it. Such a bonus is already worth a set on its own in my opinion.