O ... Kay ... Alright, let's see what we've got going on here.
Conceptually, I understand his being a counterpoint to your Keseh concept, but not every concept has a counterpoint, and sometimes the counterpoint may have been better applied in a different direction. Many of my issues with your Tuan concept had to do with with being too tanky for the damage he was allowed to do. A similar, although not the same, issue is appearing here.
See, the best tanks often do no damage. However, they often have pretty good cc to work around that. That's how support tanks in particular function, since their damage is laughable their contribution comes in the form of their smart application of disruption. Baja doesn't have any such disruption to apply. There's nothing that would incentivize aiming for him (especially if the damage he eats from his W is applied in the amount it would have been dealt to the intended target after their defenses and not his own). People often say not to shoot the tank in a fight, but there are reasons to shoot the tank. If you're the carry and the enemy Maokai is doing an admirable job of not falling over dead under your team's mad hacking and slashing, you're not supposed to close on the squishies standing on the other side of Maokai because Maokai, if he knows what's up, is going to pull you into a cc chain once you're in range of his carries. In such a case, you shoot the tank because the tank is the only thing you can shoot safely and if you can manage to kill him you can go for his friends. Baja would not be standing out in the front skirmish like Maokai or Nautilus would because he wants to be nestled in his backline to give them the full and consistent effect of his aura. So to shoot him, you're already close enough to shoot someone else. He unfortunately can't do his job because he doesn't have any peeling tools. All the protection he can provide stems simply from reductions, and enough brute force will easily make up for that if it's essentially a 5v4+Aurabot. I know he has ways to deal some damage, but it's not enough, and in any case it shouldn't be damage at all. It ought to be cc.
His passive is ... interesting. Least wise there's nothing very wrong with it. Fixed health is, however, a bigger problem than I think you realize. FireDrizzle's point is one that shouldn't be ignored. While it is true every champion, in fairness, must have its counters, it is also true that raw skill should always be able to win even the worst match-up. At the very least, you should still have something of material use to throw into a teamfight later on without automatically disappearing in a messy spray of particle effects because your counter happened to show up too. If this is not the case the champion needs looked at more closely. It's one thing to be abruptly dying in every fight after going 0/5 and drawing the particular ire of the one ass hole on the enemy's side of the map that built AP against your raw armor, it's another entirely if someone can remove you when you're 13/2 because they happened to get close enough. Cho'Gath can remove squishier targets and execute tanks with surprising swiftness, but he's hardly a Zyra counter just because he eats his veggies. By that argument true damage is a counter to any tank, but I wouldn't call Vel'Koz the Great Tankbuster, regardless of how much he hurts if his combo lands. I'd say take a closer look at how Kled functions, as he has a similar yet very different thing going on in his own passive. Some sort of, dare I say it, minigame might help to provide more consistent ability in this passive. Forhonor321 addressed that Baja can indeed achieve such levels of armor in the jungle as to render him very much untouchable until other people get more items, and this kind of early and unpreventable spike may be an issue. Also, just remove Warmog's from working on him at all. It's okay to have a dead item there, and the last thing Baja needs is the ability to quickly top off his health after a skirmish to make sure the next one lets his W tank for everyone who didn't regen to full.
The Q is interesting. A strange sort of upgraded old Urgot passive. Not really much to say on it, except that the scale could be reduced. Baja would likely build nothing but Armor, and for someone of his tankiness to be able to deal even moderate damage in a way that additionally cripples an enemy's damage output is just a little too much. I know it's his only damaging ability but even so. It's not like Braum puts down a healthy chunk of damage in a late game fight just by hitting someone with his Q. Something that does meh poke early on and then becomes negligible as the game goes would be plenty. Also, it does need a range. As little as it matters in most instances, it means, in particular, if for some reason Baja ever does need to retreat from a fight, he can still throw his Q out from safety to cripple the enemy damage output against the rest of his team without even being nearby. A long range, like the one for Sejuani's and Twitch's Es would be enough to keep that from happening while still allowing it to reach across fights.
The W is incredibly strong, and I feel could do with a minor nerf of some fashion. Maybe take away the increased range on activation, it's already putting in work from the increased absorption. Also for additional nerf have the damage apply to Baja's health after it's been reduced by the recipient's defenses, not Baja's own. This alone puts him down as a support tank since this, like most of his abilities, are effectively close to dead weight by himself, so being alone at the toplane or in the jungle simply wouldn't be optimal. Also you need obvious VFX for this. Knight's Vow is one thing, it applies to one guy, who you're tethered to, and who the enemy team can see is soaking damage. You need to somehow develop a particle effect of some sort to indicate that Baja is soaking damage from people around him and you need to have it somehow very clearly indicate when the W is activated. Incommunicability is why Urgot's old passive was dropped. It didn't matter that it was helping, no one could tell it was helping. It didn't matter that old Taric gave a huge armor buff and old Sion gave massive lifesteal because it wasn't obvious they were doing so. When it's not obvious, counterplay diminishes (enemy can't tell what you're doing), teamplay diminishes (teammates don't notice when you do it), and satisfaction diminishes (you rarely get credit because it's so unnoticeable). It's also why things like Fiddlesticks's old passive were changed. It simply didn't feel enough like it was helping, whether or not it actually was.
E is phenomenally powerful. Yes, there are other cleanses in the game but something those cleanses often have to inhibit their usefulness is their use only on the user. Baja need only activate E while charging with his team into a fight and all of a sudden the enemy Annie can't try to initiate with her Tibbers because the stun won't work. All of a sudden Nami's or Janna's attempt to reset the fight isn't gonna cut it. For 3 seconds, all the cc the enemy team has to rely on making the fight work isn't worth using. For three seconds they have nothing but raw damage to try and dissuade a fight. Raw damage that is being mitigated jointly by Providence and Baja's W. For three seconds they simply can't win a fight unless they are a very specific composition of champions. For three seconds. Three seconds is a long time in a LoL teamfight. Ever been hit by a max rank Morgana Q? That's three seconds. Note how painfully long that is. Especially during a fight. I'd say make it a single-target Cleanse. He can pick someone to use it on, too, which is already very powerful. Also a slightly longer cooldown, I'd say, to make it more possible to lane against support Baja, who by being there means your Thresh and Blitzcrank need to wait for his E to be on cooldown. Note their own cc is also on lengthy cooldowns, so Baja's needs to be nearly twice that to be fair. The passive part of it isn't particularly necessary. He's already nearly unkillable the least you can do is make it so the enemy team can maybe keep him away from the fight for a little while.
The ult is ... unnecessary. And I'm sorry to say so, too. It might have worked phenomenally if it weren't for his W and E being how they are. As it stands the Q is already a little iffy because damage reduction effects need clearly indicated (notice how obvious is it that someone's under an Exhaust, for example) and besides often suffer the problems I listed on the end of the section on his W. If he didn't already reduce damage dealt in two ways (Providence and damage leech) it might be okay for him to increase his team's damage. But he does. And unfortunately that's simply too much. If I'm dealing 10 or 15% less damage against my intended target, minus a further 25-50% that's going into the increasingly unkillable (more tanky for more providence) guy I'm trying my best to ignore and I'm taking 30% more damage from his friends, then the guy making it all happen damn well better be showing off a true display of skill so that I can rest in salty assuredness that at least I lost to a harsh outplay and not just facerolling. Baja doesn't need such skill to do that to me though, he just runs in with his increased movespeed and a cleanse to shrug off peel attempts and does that by standing next to me. In fact, he'd might as well stand there and spam his laugh because that would do far more damage to me than whatever wet noodle autos he'd be throwing in.
, but now an AURA and apply to all your allies. On top of this, activating it increases the size AND the damage reduction! WOW! I'm sorry but this is probably the part of the whole concept that I hate the most. You're somewhat pitching this juggernaut feeling character out but then throw in damage reduction from not only the enemies but also to your allies! That combination alone is somewhat broken and does not at all fit in here!
Ahhhh a good test subject
Nomnomnom
JUSTICE!
etc
