@Meddler, can Mundo get just one damage scaling?
TL;DR Dr. Mundo has low skill expression, he also happens to be the only Juggernaut with zero damage scalings. Please add an AD and/or AP ratio to one or more of his abilities to add skill expression to his build path.
has really awesome base damages, but he's pretty much the only champion left in the game that still doesn't have any damage scaling on any of his abilities. Recently Riot buffed Poppy's AD ratios, Sejuani's AP ratios, Shyvana's AP ratios, Gragas AP ratios, all to support "alternate" aggressive playstyles.
Mundo, on the other hand, has no alternate playstyles. If you want to try to build like more of a carry and less of a tank, you can sorta pick up
but even those ones don't work that well with him (except maybe
). As a Mundo main, I'm simply bored with Mundo's build options. It's impossible not to build tanky.
Q: Scales off target's current health -- Mundo's bread and butter. But if you want it to do more damage, you ... can't. Nothing you build will change the amount of damage this ability does, aside from Sorc Shoes but then not by much. (You might argue
, but I would count that as item damage rather than increasing the amount of damage the cleaver itself does.) I argue that this ability is the best one to add an AP ratio to, since it's a skill shot which requires skill (one of the few things in Mundo's kit that do) so it wouldn't be way more broken at lower divisions than higher ones.
If this ability had an AP ratio, you could finally start doing actual poke damage with it, making him useful in a siege/teamfight situation. He could also become an off-tank AOE damage dealer like Rumble or Vlad with items like
. In addition, he could potentially become a (still probably off-meta) support with some AP 
like Zyra or Brand, but also with the option of going tanky and getting
if he's not snowballing.
W: Has 10% AP ratio, but a VERY short range and a super high health cost in the early stages of the game -- if you get first blood and make it back to lane with an extra amp tome, seems like you should be rewarded for sticking to your target -- but even if you stick to your target for a nice, long 5 second trade, with your W active that whole time, you've only done 20 extra damage with that 435 gold purchase. On top of that, its negligible range (160, less than some champs' AA range!) makes it hard to proc, and its high health cost means you're doing essentially the same amount of damage to yourself. Especially if you max the ability, in which case you're losing way more health than it's worth. This ability grants tenacity and a bit of extra damage, and already has an AP ratio, so I support leaving it alone in favor of focusing changes on the other abilities.
E: Scales off Mundo's max health & missing health. I like this ability, sort of a better version of Olaf passive IMO. However, a bonus AD ratio would make this ability really shine -- something like a Garen Q where it's not crazy but Mundo has the choice of building a
if he wants to bully his laner a little more. Adding one AD ratio could potentially open Mundo up to a lot of different builds -- predator assassin Mundo with
, finally viable bruiser Mundo with 
, and more.
Alternately, you could double down on making Mundo a magic damage dealer by changing E's damage type to magic, and giving it a smallish AP ratio. This would really cement builds like
, similar to a Vlad or Rumble build.
R: Scales off Mundo's max health and gives bonus MS. If this ability were also given an AP ratio -- probably for a FLAT amount of healing, not for % max health healing -- it would really cement the AP build by making Mundo a little more tanky (necessary since his abilities have health costs and short ranges) while allowing him to build AP. It would also put more skill expression into his kit by requiring better timing to use, since he'd be overall less tanky and there'd still be a health cost on it.
(Alternately, you could add a % damage reduction per AP scaling, like current Gragas W.)
To wrap things up, I just want to remind that opening up Mundo to AD/AP builds will NOT make him as brokenly OP as simply buffing his already-high base damage, healing, or max health ratios. Because of Mundo's short ability ranges and low mobility, he has to stand in the very middle of the fight to get his abilities off. Building AP will render Mundo squishier, so as long as the ratios are appropriately tuned, that would be an appropriate risk/reward.
and 
and