Any tips for beating the boss of the Void Quest (trying not to give spoilers).  I can defeat his first form pretty easily, but can't seem to stop him from recreating it.   My party contains the original four characters, and I'd kind of like to keep it that way if at all possible.  Any ideas?

Void Quest boss was easy. He will change into his first form several times, but you can still wail on him when he's not. 

What is your level? I tried it at 42 originally and had issues got him close but he focused "Charlie" down and I got pissed so I leveled to 45 and had no problems. Also all I can suggest is fuse something GOOD my trick was Power Charge, Attack Buff and Blade of Fury and that was doing 400-800 per hit to him and breaking him when he rebuilt after he leveld up so he never got the shell again; I used the original set of characters as well and only did this a day or two ago. They also all had their elemental damage 25% increase and were doing significantly more damage. Void Quest was the only dungeon I had to grind a few more levels out on.

that might be the problem then.  I think my guys are high 30s at best.  Trying to clear the dungeon in one day I think is the problem because I'm ending up rushing past the last few floors of enemies in order to clear it to get the plot moving.

Hmm I can't really remember that well but buff yourself up debuff him, use mecca leaves (200 hp to your whole party) and use your stongest attacks when you take his first form down (don't forget about attack items)

Yeah, don't do that.  Switch up your party.  It saves hugely on SP and since EXP scales you really don't lose anything when you change out members (I think like P3 it has the elastic effect where if the MC is of higher level than other characters they gain EXP faster but I'm not sure).  I basically would use one party to get up to the top and another to face the boss and do the second run through.  Sometimes the first party for the first part and the mid boss and the second for the last few levels and final boss.

High 30s? Yeah, you definitely need to level your guys up, I was at level 45-48 when I got to this boss without grinding. 

Also I don't know if you are re-clearing dungeons for the end shadows but you really should be doing that; you gain amazing experience, yen and an item at the end. There is no point in rushing the game as its gonna be atleast 70 hours of play time and instead of making bosses harder on yourself take it a little slower. I haven't swapped out guys at all really; don't wanna spoil it but should of swapped around a bit, maybe if I do the side quests i'll take some of the neglected people in...lol.

 Beat him today.  Trick was getting Black Frost (drain fire and ice, high damage fire attack and double magic attack skill).  I beat him at 41 or 42 after grinding a bit with the new persona to get Agidyne.  He went down no problem with the added levels and new persona.