Ok, so you think that SS is fine. Alright, you have played a tanker to the endgame.
One question remains though: Have you played other ATs to the endgame? Maybe you have, but then you'd have to wonder why especially the flying Inv/SS tanker build is so [censored] *clunky*?
After my tanker burnout i tried another AT and played him to the same level like my tank (in *3 weeks* mind you, my tanker took about 2 months! But that's a different issue).
A claws/regen scrapper. Both of his powersets just "flow" together. He's pretty much how'd you imagine a Scrapper in comics: Fast, quick moving, little downtime, depends on "undoing" damage rather than resisting it. And with a few defensive picks from the power pool, he becomes a light tank easily, plenty of +def powers and at least one +res power in there - which alleviate some of this "weakness" easily.
He's got mobile status protection (one even *passive*!), high damage cone attacks, 2 (!!) decent ranged attacks (he's really just 5 yards short of a blaster - literally!

), a PBAoE, stamina "built in" and plays just - smooth. I picked flight with him, and I *love* the "dogfights" he can go into against flyers. His ranged attack is quick to execute, does high damage, and knocks down 100% of the time. Runner woes are a non issue for him. And useable from the ait roo!
Then take the classic: The Inv/SS tanker with flight. A concept so widely regarded as "superhero" that even in parodies a typical "Superhero" flies, is super strong and very resilient.
But just the classic is the most clunky build available! Click on flight, and loose access to a whopping 3 powers, becuase they "only work on the ground": Unyielding stance, Hurl, Footstomp. Wee! Dogfights? No chance, many fliers, especially high level ones, have status effects out the wazoo - take it to the air, you're likely the first one to pummel to the ground. No grabbing something, flying up and hurling it, since you need the ground for "ammunition". You stand down there in US and rooted and have the flyer pelt you for eternity with his ranged attacks. No PBAoE in the air, there's nothing there to stomp. My scrapper with spin on the other hand....
Then, Handclap + US and Invincibility: Invinc gets stronger the more mobs you have around yourself. Handclap is a no-damage PBAoE with knockback and a stun. When you use Handclap while USed and Invinced you're off *worse* than before using the power because everything flies in every direction and start to run (while stunned!) into every direction because it's now also outside Invinc's aggro range, and you're rooted and your defense and tohit numbers plummet because all the mobs are out of melee range. Drop US to run after them, their status effects will affect you and you'll likely take lots of damage.
Rooting status protection is a paradox anyway: "Hey villain, to protect me from your root, I'll root myself, hah, and now I laugh at you cause I spoiled your plan! Hahahaaa!"
Reminds me a lot of the guy in Mystery men that could turn invisible only while noone was looking. A self-defeating power. Woot.
Then SS gets a damage buff that has the potential to get yourself killed especially in those cases where you need it. Can be mitigated by US and Unstoppable. And we're either back to the paragraph above or we need to switch to the final power in Invul's set: Unstoppable.
Which almost kills you every 2 minutes and gives you a lot of what you have already plenty of: Resistance, plus a stamina rec boost, and mobile status protection. Most take it to get rid of US's root, but it pales in comparison with other level 32 powers from other powersets. It's really not that great but the best (and only!) alternative to US you have. Another power that, unless heavily slotted to make it permanent, hinders you more than it helps. US does more damage to you by itself than the entire fight would ever do! For a power whose primary purpose it is to mitigate damage it does an awful lot of it!
And Unstoppable alone - unlike nova or the like - does not defeat a single mob. And it's not even really needed against anything even con or con+1.
The entire build manages to completely fall over its own feet, continually. I doubt there's as much self defeating combinations in powersets as there are here. Inv/SS tanks don't fight the environment, they fight their own shortcomings. That's their biggest challenge. The amount of slotting/planning to make this particular build even *work* is mind boggling - and, IMHO, outdoes any (certainly valid) complaints about underpowered powers from other sets (across ATs) in severity.
The Inv/SS tanker is "gimped" by default. And all the suggestions made herein barely touch the surface of what's needed to make the character "play smooth" as Krunch so aptly put it.