It feels like the painboy has a very short melee range, which might be causing issues in combat. I haven't played painboy as much as I would like to though. I think once I get in the swing of it and sort of a mid tier painboy things would be alright.

Making orks one shotting people isn`t a good idea. Everyone dies fast enough to melee.

Accurate Ork rocket launcher....doesn't sound right.
As for their AV capabilities I believe at one point they said that they wanted orks to feel much more melee heavy than other factions and that they should rely a bit more on their klaws for AV.
As for ork melee weapons being better than space marine melee weapons...its a chunk of electrified pig iron versus an axe that emits a disintegration field. In any other universe it would be laughable uneven. The only reason it might be even in this universe is because Orks think its even or stronger. Honestly, I'd say it should be weaker but have mods that reflect the fact orks think it should be better, like a penetration mod that surpasses even a modded power axes focusing on penetration. A club that has 1.5 times the durability of a power maul when modded. Stuff like that shows that a stick isn't stronger than a space mace, but an ork that thinks those wires strapped onto his stick might just make it stronger than the aforementioned space mace. For an ork seeing is believing and believing is seeing.