Except nobody needs an under-geared tank.
You want pieces with P.Def, M.Def, elemental resistances and whatnot. And a good shield. And preferably, a weapon with skill/resistance/CON bonuses. And those don’t come cheap. So yeah, losing durability at a slower rate would be nice, because tanks tend to get hit a lot.
Need I remind you that dedicated tank builds tend to be quite bad at solo-farming stuff to sell and are often noticeably worse off in terms of budget (unless we’re talking tank+squire who is better off just selling his services AFK and not tanking at all)?