You act like those are mutually exclusive. Tanks, lightning rods, whatever. Fucking Conrad or Dahlia can accomplish more than Gellius in the right conditions.
I've said before that Gellius wins in a battle of attrition. But to say he's the best tank in every situation is completely wrong. Again, if you can safely DPS the fuck out of something before it can kill anyone, then Gellius is not your answer.
Get a fucking clue already.