Fighter damage reduction is too Strong.

90% damage reduction is way to high. I'm a fighter main and I'm super okay at this game. I've fought a few high damage reduction fighters with pretty good gear built around damage and even if I get 4 or 5 hits over the other fighter he kills me and still has 40% health.

I have no idea how other classes are able to deal with that. Am I wrong for thinking high damage reduction is OP? Is there a way to deal with it that I'm not aware of?