Don't get too excited. An R with ATK+ is barely better than an SR equivalent with no useful stat on it at all. Most of them will have at least one stat that is marginally useful.
I found today that with 3x maxed affliction rate up and Mordred's affliction resist down, ATK/DEF debuffs will still occasionally miss on same-element. It's pretty rare and seems about as likely as affliction resist down missing. Which is good news, since even if affliction resist down misses you still have a good chance to land the others.