For RW, I think his breath is fire based. equipment that reduces fire damage might be ideal. He uses immobilize, so jackboots may be in order.
The best defense armor you can get helps always
Don't remember if he pierced block, but if he didnt, then you might want to train shield block licences to help.. or just in general. Shell and Protect help a bit, but he acts pretty fast, so you may not have time to redo them mid battle.

He puts out some nice damage when I try him in the mid 20s... barely able to keep up with it at times, but if you head past Giza to the next city, you might get a little better armor, then come back and kill him. He's a rough monster when you get the bill.

Same for Gil Snapper, except he is a little weaker in my opinion... except for his last 20% where his speed seems to increase.