For those still looking for help on Goku (epic mode)
Devil sword is still the best because you can recover MP, I went into the fight with about 10 antidotes, 17 Life Waters, and about 6-7 Ethers
First part of the fight just don't let him knock you low, put on Protect and drive through his physical attacks with seiken and use your mage to heal if necessary.
When you get a little about 65% he will use a magic attack which effects both users and so you might want to make sure you have barrier on at this time. When he first began attacking us both I would use Power medal at first (because he didn't harm me that much) and then Judgement him with the mage, if getting to low heal your fighter.
I use the Andidotes later on when he seals the two characters, because this spell does minimal damage I would just make the fighter use and antidote on the mage and have her cast judgement and not worry about the fighter just yet. Because when he really starts to use seal alot if usually when his spirit bombs are firing off the WAZOO so by the time you cast judgement, then go up into defensive mode, the seal will have on its own fallen off your fighter. Remember to constanly use Power Metal and Healmore "if needed" after a spirit bomb, if you still have high health and he focus's on the mage, keep using judgement. WHen it comes to spirit bomb time you will have unlimited MP at your disposal.
I also use the antidotes if the poisen he uses becomes too much, at first I ignore the posien because when barriar is on it does small amout of damage, if you can save your antidotes for his sealing frenzy at the end, but if he stacks teh posin a good "2-3-4" times, I would use and antidote and quickly use healmore to cure yourselves.
Water of lives come inhandy when he focus on teh mage as well, there were a few times at the end, (btw I beat him with this move) he will focus on the mage and quickly knock her down to low 1000's while the fighter is still in his 9,000's THIS is when I will use a life water on my mage to heal her all the way then cast judgement hurting Goku for 21000 while ending your turn with almost full life on both characters.
Hope this helps