Just use a Rage All Denpa, wear Light Bracelets, have high Dark resistance (max preferably), buy some new clothes, have a Heal All if you can, and bash his head in with physicals. He eventually loses his weakness to light, yeah, but he won't have much HP by then. Adding Excite All, if you want to risk it, isn't that bad either.
If nothing else, grind more. I beat him easy with people 40-43 or something like that... with said strategy, mind you.
Ar Rappy of the PS0 board | Rappy Souls: 1054 | 3DS FC: 1590-4884-9269 Sage of The Denpa Men: They Came By Wave board ( http://i48.tinypic.com/20gmued.jpg )