This question is difficult to answer. Endgame, a dex-based sin with pretty low hp and def is one of the tankiest chars in the game with 75% block and like 70% avoid. Look at the same sin early game, when you have low block, and low avoid, and you will cry. Now look at a barb. It is insanely tanky at early game, thanks to the tons of def it gains from passives, can get really decent amounts of life (and phys reisst) with small investments, but lategame, defense definetly falls off a bit, and has no block or avoid. Do note that with throw barb, you can reach decent block chance, but throw barbs are not that popular.