By no means is AC bad, but it particularly doesn't press any unique advantages of the hero in the case of that game. An MKB at 25-30 minutes with a Blink would have let you kill a lot of solo heroes and keep snowballing, and eventually would be insurance against the Medusa.
Also to be borne in mind is that a miss on that Butterfly could be a missed bash. That's hugely crippling lategame.
So I should have gone Treads - Armlet - Blink - MKB - BKB - Heart?
Surely the loss of attack speed with punish you late game?
Aren't bashes always truestrike? At least sniper's is.
No, it goes through magic immunity