Shadow Assassin Kayn buff ideas

Shadow Assassin Kayn can run away with a game if he is extremely ahead but I think he's fairly weak when it's a "going even" or behind situation. IMO here are some of his issues:

• Can't fight anyone with armor / HP even when ahead.
• Not that slippery like other assassins because of the delay after he does his Q where he's stuck in place
• While his passive does magic damage, it's POST mitigation damage, meaning it's magic damage that you can build armor against.
• Can't ult anyone he hasn't damaged, drastically limiting his escape options in team fights.

IMO they should make it so his passive does pre-mitigation magic damage so that he can at least go toe to toe with someone he's ahead of that's built a chain vest / tabi. It's impossible to carry a game on shadow assassin if they have bruisers because he just can't kill them at all. Q should lose the delay if he's in shadow assassin form and IMO he should just be able to ult whenever / whoever without having damaged them as long as they are in range. Those are fairly minor buffs but I think they would go a long way. I have trouble even when getting fed on him to carry games just because of these issues and it seems with everyone going rhast, that isn't an issue specific to me. Shadow is just too weak compared to Rhast to use in a competitive environment against real team comps.