The pro opinion is that Greenskins are indeed weak. But you gotta take that in context. In Very Hard+, when you're playing them, their units are not very strong against Very Hard+ buffed melee troops. They're cheap but they're kinda shit.
Having been on the receiving end of da Greenskins though....when they've got a couple WAAGGGGHHH stacks accompanying their armies, Greenskins can be kinda tough. You'll be outnumbered and they'll swarm you with melee and swamp your lines, force you to micro the crap out of your cavalry, etc.....If you're doing a face roll army, facing off against a face roll AI, then yeah, they're not too tough. But when you've got a finesse army, dealing with an entire army that does not give a fuck and swarms you, it can actually be quite a bit of pressure.
Pound for pound, unit to unit comparison, yeah they are kinda weak. But I think it all comes together for them when you consider WAAGGGHHH stacks and WAAAGGGGHHH buffs.
Also, you're playing Khemri or Tomb Kings or w/e. Your skellies are one of the most disposable units of the game. "sure I had a decent amount of losses" makes sense when you consider you're sacrificing T1 trash troops. Imagine being an empire player and paying out the nose to have your half your expensive army slain by low tier ork troops due to their massive numbers....then getting clobbered over the end turn by the 2+ WAAGGGGHHH armies following it up.
FWIW, after watching dozens and dozens of hours of LoTW playing, my impression is that most armies use the same AI. There's nothing particular or specific about the Greenskin AI, it's just the overall army composition that dictates how the AI will behave.