All those champions, that you described are balanced and some might consider weak
has one of the worst laning phases out of all the AD Carries. 1v5ing as Vayne is pretty near impossible unless you're Doublelift or Imp, her damage output is irrevelant until she has 3 items.
has a decent laning phases, good teamfight potential, decent dueling, but her damage output late game is ridiculously poor due to her 90% AD scaling on her autos.
has poor AP ratios, and his skillshots are really slow and easy to dodge.
say Hi! to
, if you fight Tryndamere while his Fury is high, that's your own darn fault
So let's see here, Let's say Yasuo has 100 AD, and his mastery is that 15% lifesteal on crits, mmkay? Steel Tempest is on a non-static 4 second cooldown which means it can be reduced by CDR. Which is pretty insane right? Let's factor in his stuff.
Assuming that he has
and
which brings him right up to the sweet spot of 100% crit chance due to his passive. Now, assume he has 5 points in his Q, that's the flat 100 damage plus the additional 100% AD scaling which brings it up to 200, bring in the crit (which is scaled to 75% on his Q) and that brings up the total to 300 damage per Q on one target. Factor in the free life steal and that's 45 heal per Q, multiplied by however many enemies you also hit. That's with only 3300 gold and with no damage items built. Yasuo is broken right now, especially because of the Marksman Meta, and how assassins counter Marksman so well. Which he is good at diving because of his passive shield plus Ult, and dash.