While I would say this is a champion I'd play if they were in the game, I do have a handful of concerns.
First with clarity concerns:
About the passive on his E, that's the only place in this concept where I received a hint as to what resource he uses. Care to assure me that he uses energy and not other resources or is resourceless?
The wording on his R seems a little odd, particularly the last point of it. Since he's able to cast this ability on himself, would he get both of them when self-cast or would only the one aspect be used? Also I'm unsure of how either aspect would be decided.
Regarding his passive, I can see a TON of value in that ability, too much to feel comfortable. Have him buy Warmogs + Spirit Visage and suddenly all nearby allies late game have a +150 at the right of their health bar. The damage reduction per nearby ally/enemy champ is also incredibly powerful alone being able to reduce the damage he'd take by 45% with minimal effort required on his end. The part where allies at full health gain bonus damage seems both tacked on and very finicky as so much as a minion attack against any of those champs will cause their damage to decrease and it would be nearly non-existent in teamfights. Gaining bonus movement speed when near an ally seems to be the most reasonable of these for a tank/support, so no complaints on that aspect.
His Q seems like an ability with an insane ability to scale into the late-game while still being something menacing in certain abuse cases. It gains stacks upon the boosted target dealing damage to any target, so a champ like Morgana or Brand could W a group of minions and gain 20 AD+AP with a single spell at level 1, and that free Amplifying Tome worth of stats can do a lot that early. Any tank with Sunfire Cape or Cinderhulk could stand in the middle of a minion wave and stack up a ton of free stats by doing nothing. Even if you look at more conventional bot-lane combinations, someone like Sivir would get 20 stacks from casting her W into a minion wave and there's minimal counterplay options for Marksmen aside from hoping their support lands their 1 hard cc ability (assuming they are a champ that has one). And while most champs don't make much use of both AP and AD simultaneously, the few ones that do get much more value out of this ability than others, such examples being Ezreal, Jax, and Kayle.
His W seems like a much more beefed up version of the Bond of Stone mastery. Combine this with the damage reduction on his passive and he can effectively peel for an ally in a teamfight without needing to worry about his positioning or actively keeping them safe. Again if this ability were to be used while he had Warmogs + Spirit Visage he'd be able to heal all nearby allies that were below 50% health on cooldown without worrying about his own health. The gold generation on this ability feels as unnecessary as Ashe's gold generation on her old Hawkshot. As a support main I know supports don't make as much gold as other roles, but support items are balanced around that fact and it looks like this champ still has enough synergy with the gold generating items to make this passive an unnecessary free source of power. And while I'm all for abilities that can be cast on allies, this ability does literally nothing for him in solo lanes outside of ganks, of which a defensive boost probably would be negligible more times than not.
His E active seems pretty fair. This ability could be broken though because of unknown numbers such as the range he charges from and how far back they're sent, but number problems on champion concepts are the easiest thing to remedy so this ability seems pretty good.
His R seems like a very polarizing ability. If he granted himself the 80% damage reduction and there were 4 champions near him, he'd be invincible for the duration via his passive which doesn't seem right since he'd also be absorbing damage via his W that would be negated entirely. Then there's the notion of misplay potential, being that you could reduce the damage a carry on your team deals while increasing the damage you (a support/tank) deal, being about as trolly and unfortunate as a bad Bard ult.
It seems like the overarching problems in this kit stem from some easily identifiable places, namely versatility and reliability.
First, he seems like a good combat generalist having durability (P), a heal (W), an offensive steroid (Q), hard cc, the ability to buff allies (P,Q,R), a movement speed boost (P [E?]). Considering how he doesn't have waveclear, neither significant amount of cc nor mobility, not having mana limits his ability to chain his abilities together while restraining build options, he has questionable engage potential, he doesn't seem like he'd be able to reliably trade with anyone alone, and he lacks the ability to thrive in solo lanes makes it seems like there are still some weaknesses to this champion which are good. It's also nice seeing a clear itemization path as his innate damage reduction provides him the room to prioritize health/regen over armor/mr. But when he's in his ideal (or even a standard) state, that being near an ally that can deal lots of widespread damage or quick damage, then his potential outclasses many other supports. Coupled with the fact that all of his abilities are either auras or targetted, the room for errors/mastery of this champion seem minimal, and minimal room for errors often means there's little room to outplay the champion in question.
There seems to also be a handful of unintended and unenjoyable interactions his kit opens the potential for. Aside from the Warmogs Visage interactions I listed above, he could take Smite and walk into the enemy team as they do Dragon/Baron, ult himself so he becomes invincible, then smite it when it's low enough. He can make an ally nearly invincible for a duration by ulting them, giving them his W, and the health regen from his passive would keep them topped off post-Warmogs Visage, while simultaneously having the ally in question deal negligible damage.
Should this idea be refined, I'd recommend making the passive to be comparable in strength to other passives in the game, add more engage potential/cc to the kit, make aspects of it less reliable (ie Instead of Q increasing a targetted ally's damage, have it be an on-hit/skillshot that would decrease an enemy champion's resistances [and if you're in love with the idea of it scaling over multiple hits it could increases the shred per subsequent auto to a cap]), and ultimates that are double-edged swords are things that can be difficult to make worthwhile, especially if the person on your team being inhibited isn't the champion casting the ability. Giving this champion mana would open up build options as tanks tend to enjoy items like Frozen Heart and Righteous Glory, and the active of Talisman of Ascension could be useful as well, very rarely would a champion without mana want any of these. And noting whether abilities scale with AP, health, armor, mr, or don't have scaling would be beneficial even if you don't provide numbers or include how they scale with skill points.
