I am sure things will be tweaked somewhat, eventually.
I have never liked it when they simply added a game mechanic universally without consideration for specific situations.
However, this is supposed to be a difficulty s hard that only the easiest reaper settings should be completable by us currently.
We should be slowing down.
Should be backing up and trying to figure out why a certain attack is not working, and if we can find an attack that does work.
We should be relying on team-mates and everyone working together to defeat monsters.
I am assuming that the DR buffs you mention are not on every monster?
I am assuming that they just come up on a few random monsters over the course of a dungeon.
This does not bother me at all.
There was a time, when I specifically tried to carry weapons of differing damage types.
There have been times in the past, when I used a weapon that the base damage wasn't effective against what I was fighting, but the extra damage type it did was doing some damage to what I was fighting.
I didn't totally like those situations, (really wished I could access my bank or mules inside a dungeon to find an effective weapon) but I was entirely on the Dev's side for creating that challenge for me(us).
I realize some builds (like any Warlock) never have DR issues.
I think the Devs need to add things that give them trouble; not remove things that give other builds trouble.
An interesting, challenging game has variety and every build has a time to shine and a time to ask another superhero to take care of the guy with the Kryptonite.