Deine is AWESOME, with 816 base defence (more than enough for most things) and 2.6k attack on skill. Gellius, for comparison, has 576 base defence (less then Bernice's 595!)), but monstrous 3978 health (and 306 attack, and 10 MR), has shining 1.15k defence on skill, so he does serve better as a wall with his skill on, but Deine serves as well, all the time and simply crushes anyone who opposes her.
Gellius truly shines with he receives SAW (what we don't have) - with it he becomes true adamantine wall, with 1728 defence, 30 MR and 5 block. A supertank for superbosses, indeed.
DMM-side Deine recently also have gotten a defence multiplier in her SAW, to complement her AoE 3xPower attack, I believe, bringing her to comparable defensive parameters...