Ragnarok Orc Hero

Is there some gimmick you gotta do to damage him normally with X-attacks, like have at least 1 party member hit in the back while you distract, or something? Or does he just have a simply unpassable massive X-attack damage resist?

Cause the last time I tried him on my monk, my usual X's of around 500-900 range were reduced to 50-60, and I had to spend around 30-45 minutes grinding him down with skill spam and roughly 1000 (not kidding) Z attacks

No idea but there's no way in the world after beating him once I'm doing it 30 times, it's not even difficult it's just a level of unemployment I don't have