I don't mean to sound harsh, but I doubt you'll ever get Diabolos at your current level, reason, its just too hard, even with a full party of 70+ ever since the magic resistance implement. You'd have to pay a pretty big amount of you wanted it and wanted to leech it, and thats if its even possible anymore.

Edit: diabolos also draws you in now,you used to be able to stand on the ledge and nuke him and just have the tank drop down to provoke him, but now he'll draw in all your blm's.