Garen
The primary issue is the tool-tip for his Ultimate, which reads something like:
...dealing 175 / 350 / 525 Magic Damage, plus 1 for every 3.5 / 3 / 2.5 Health the target is missing.
Can this be changed to
...dealing 175/350/525 (+28.57 / 33.33 / 40% of target's Missing Health) Magic Damage.
And the second thing is his passive.
Garen will regenerate 0.4% of his maximum health every second if he has not been hit with an enemy ability or taken damage from any source (excluding minions) in the last 9 seconds.
Dr. Mundo's passive is
Dr. Mundo restores 0.3% of his maximum health each second.
Since they are both tanky manaless champions that sustain through things... Can Garen's passive get some buff? For example; reducing the reset timer or increasing the health per second; or making it take time to deactivate; have the reset timer be reduced whenever he deals damage, have it not be turned off by passive auras (Sunfire Cape), maybe making it a 'resource'--
After not taking damage from Champions, Turrets, or Monsters for 9 seconds, Garen generates 2 Resource each second. If Garen has Resource and is below 85% Health, he consumes 1.33 Resource each second to restore 0.4% of his Maximum Health. Maximum of 14 Resource (+1 at level 3/5/6/8/10/11/13/15/16/17/18, +2 per rank of W).
Perhaps you could even make Garen's Perseverance not so severely gimped in the jungle (reactivates sooner if being damaged by a Monster, say 5 seconds instead of 9), and we could see him roaming the rift that way (heck, I know I want to see more Garens in bushes that I haplessly walk into, if only because that means that Garen's seeing play).
... and why does Courage have a 24/23/22/21/20 second cooldown, anyway? Would it be unreasonable to ask that it be lowered to 20/19.5/19/18.5/18 seconds (or at least flattened to 20 at all ranks), since mistiming the shield slightly is difficult to make up for when laning (at least, with the current Perseverance).
But really, if I'm being honest, just the first part of rewording the ult to say that it scales directly off of a % of target's missing health instead of 'dealing 1 more damage per N health the target is missing' would be wonderful for new players to be able to grok him quickly, that it is to be used on enemies below certain health thresholds.
..and can Deathfire Grasp be put on his recommended items already, with some AP ratio added to his kit?
and it gives him massive bullshit drain tanking abilities.