Change to Crit Keystone mastery
In it's current state, I find the Warlord's Bloodlust is pretty completely useless. There are so few champions that can crit with any reliability early game, 
and 
being notable examples. Yes, I understand that getting 15% of your crit damage every 2 seconds and an attack speed buff off of minions is broken, but only having it proc on champions makes it borderline useless. Death's Dance has the same ability (minus the attack speed) while also giving you combat stats and burst resistance and it works on non-critical attacks as well!
From my experience a lot of players hate Yasuo because of his crits and I can understand why the mastery needed to be nerfed, but it was nerfed too far. Even when trading with an opponent, you'd only get 150 hp back if you are critting for 1000 damage, which is quite high for critical damage in my experience. That heal is also on a 2 second cooldown that cannot be reduced. If you were to stand and auto attack an enemy champion long enough to proc the mastery twice, you'd have taken far more damage than you'd heal simply from their own attacks and whatever minions happen to be around. Simply put, buying a Bloodthirster would be an objectively better purchase because it gives you more sustain, a shield, procs on minions, and gives you AD. The only champions that it's even worth while taking Warlord's on are marksmen that build heavy crit because they are the only ones who can reliably and safely proc the mastery.
I have two suggestions to make the mastery viable again unless you are playing an ADC geared towards late game.
- Remove the cooldown on the passive. It would also be reasonable to lower the heal % an amount if that were the case, though I will not pretend to know what a suitable one would be. My reasoning is that you'd have to bank on random crits unless you have 100% chance of getting them, so getting a more tangible reward for the risk involved would be a worthy tradeoff.
- Allow the passive to proc on minions but be at a reduced rate and still consume the 'charge' of the passive, causing it to go on cooldown again. This reduced % would be something like 5% damage dealt maybe even slightly lower, but the point is that it still gives crit-reliant champions a viable sustain option.
From my personal experience with the game, I find that these would be worthwhile solutions to the current lackluster nature of the mastery. Personally, I think the second option is better, but that is my opinion. Speaking of opinions, I would love to see yours in the comments if you have one. All I ask is that you be respectful and provide meaningful discussion, rather than stating an opinion or an anecdote without elaborating on your point of view and reasoning. Please, if the only thing you have to say is that my idea is stupid, please simply pick the 4th or 5th option on the attached poll.
~~Thank you and have a nice day! ~~MorningEspeon