I've just replayed the entire game up to this point (and still love it, but I forgot how much grinding is required...)

Sadly, now that I'm at this point, I find that I have no motivation to keep playing, to figure out how to beat these guys.
I'm currently at Level 80 (I just discovered that you can use All-Reflect on the High Beast Lord, and I beat him the second time at level 80, and updated my walkthrough to show that information.)
Everyone has the highest weapon and armor but only at +1 or +2. I used some of my DM Points that you earn through the game to buy some of the needed crafting materials, and now I have to grind to get the rest.
Does anybody have strategies, or remember what level they were on or what equipment they had, for fighting these guys? (i.e. do I have to grind to lv 99, or would 85-90 be sufficient?)