Yes. Yes. Immortal Builds are good IF only 5 or 10 Users using it (for extra challenge) but if so many in Arena especially Eternal Lair, the Arena will be boring. No good fights, always frustration.
I love to fight tanky builds but can be killed in just 1 full round like Bodom (Warrior) and Dark (Wiz). But facing Immortal tanks like Hell_Scream (with 470k HP 800 Power) I got kinda bored.