54367
I love mundo so my opinion here is a bit biased, K there is my disclaimer :-)
Mundo's passive despite what everyone keeps saying about "he can have it during combat" doesn't do much for him. In combat his passive may let him take one more AA... so what. Being a tank he's trying to take 20+ aa's and one more might matter in 1 out of 200 mundo fights.
PLUS it's being compared to Garens passive which relates but is not really compared properly as far as game play goes so here;
1st) A Mundo ults during a teamfight in an attempt to tank as much dmg as possible for him team and gets out of the fight with 100 health. He is done fighting till he can B and return or till his ult is up, His regen is not enough to rejoin a fight.
A Garen goes into a teamfight and comes out with 100 health and stands in a bush (there's always a Garen in the bush) and will regen more than enough health to come into the fight at the end and clean up all the enemies that survived or turn the fight for his team.
2nd) In lane a Mundo trades and has enough regen to trade and not come out behind as long as he doesn't get to close, His choices are farm minions and harass with cleaver for even trades or farm with cleaver and stay to far back for them to harass.
In lane a Garen constantly pushes the atk hitting you with his dmging silence and spinning on you tearing your life down so you can't get away because of the silence and have to take a huge loss of health from the spin. If you are good you can win trades and drop him to low health while only losing about 1/4th of your health. So Garen disappears for a little while and comes back to do it again before leaving now you are around 1/2 health for his next assault. A Garen wears you down in lane early and constantly. You can't chase him down for the kill because mini dmg will kill you if you press to hard, and his cooldowns are low enough (& free) that he'll get to combo you first FTW. O and when Garen gets you to around 50% health he will just be in the minis farming (sometimes taking mini aggro for lulz) denying you farm since you can't get close without risking a death from his combo so after two encounters you lose farm and lane. With few champs being able to do anything about it.
TL;DR; Garens passive, safe laning, ability to get in and out of a fight to rejoin it with full health has made him better at mundos job while being safer with more dmg. Mundo isn't bad but his passive should have been buffed too since health regen is Not a combat stat. It really only helps in the lane phase and after combat and it's mundos Ult NOT his passive that gives him enough regen to stay in a fight or in lane.
O and also as you are trying to think that Garen only starts out .1% more regen pls remember; Garen has more base and scaling health so it's more than just .1%, the only time regen matters is out side a fight, Garens % Doubles at lvl 11, unlike Garen Mundos pre-6 laning isn't very good making him prone to loseing cs/lane, and unlike Mundo Garen scales with AD making this like black cleaver Devastating. Mundo isn't bad, he could use a little love, But I'd hate to see them do to Mundo what they did to scion... there is no scion anymore, he died and his evil genetic clone took his place. He's not even the same champ.
isn't 
;)
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anyone?