in my opinion tankiness and damage dealing shouldn't go together apart from extreme cases like 60-min
or
, but anyway.
The best one that fits your criteria is
. Very tanky (hopefully you'll build him as such), sustain in skirmishes and teamfights, and he hurts, like a lot, passively ignoring partial armor which syncs super well with
, with a true damage dunk. Enemy team cannot ignore you because you'll blow them all up otherwise, but focusing you is a problem in itself since you're tanky and can heal back up with a simple Q. His obvious weakness, though, prevents him from succeeding in competitive plays: melee without any gap closer or hard cc. Be wary of top
or
; they will make you suffer.
Edit: I realized I left out the mobility you asked for, but really, mobility, tankiness, and damage? If such a champ (tank
cough cough) exists everyone would be playing/banning it @_@