tank builds should be unkillable as thats all they can do is tank,and burn sd i guess.
but sm whos tankier then tanks thanks to healing when teleporting +sb is just insane tankiness´,and that lets them do it in top dmg gear.
the typical zutto effect as well where hes 7k hp when he foods up and can 1 hit my rf from 6500hp in full dd 380 gear +12,being a tank and having the OPTION to also do that much dmg in 1 hit is insane for most pvp encounters we have guild vs guild, the sm problem is roughly the same except they do faster attacks but kill you as fast if you stand still,and most of us have to to hit them.
also the unkillable gms are unkillable tnx to how good they play,and how good the 2-3EE supporting with sd are.
the unkillables die often if you get them to stand still.