King Arthur Joust Hybrid RAAAAAAAAAH

No offense, I wouldn't build crits on him. I think this build might only be working (90% win rate as you're saying) at lower levels...don't think it'd do much against more solid competition. You're really asking to be blown up with this build.

Also, building Rage 4th item is a fair delay for an item you want stacked, though I guess in Joust you might stack it semi-easily.

I'm thinking you don't understand Arthur's basic attack limitations:

• Lifesteal: As it's an AOE, he only benefits from 33% of the lifesteal. Asi isn't great, though Soul Eater is at least helpful because it gives ability lifesteal, providing some sustain to his normal use.
  
  Attack speed: his basics aren't affected at all by AS. Building Asi, you're completely throwing away that stat.
  
  Crits: believe that AOE affects his damage with crits too...1/3 the total damage in those cases.

With Arthur having so much ability use, you're sacrificing ability damage options, and while you have a couple tank items, there's little utility in them outside of the protection aura. If you want more damage, grab some more CDR and pick up Heartseeker or something. Just don't go with this build.