I think you have enough good units that you can do it!
So first thing is again, if you're not going for the esper mission, then it's probably not worth the trouble. Other than the staff, there is nothing special about the rewards.
I think the best way is to bring a FF-0 unit with Summon Eldon (I think you have Queen 7*, right? Rem works too). He's not too bad before the 50%, so just get that mission over with first. While you're at it, try to whittle his HP down to, but not below 50%. Once you get your 2 espers out of the way and he's at 50~60%, then prepare for the real fight by casting re-raise, buffs, etc.
If you haven't already, make sure all units are confuse & paralyze resistant. You'll also want a stop resistant unit.
If you need a chainer, use my Ang. If you use beast killer arrows, that's another 75% buff for 3 turns, and if you double arrow the armor piercing arrows that's a 10-hit combo you can chain a magic finisher off of. The killer bow I have on him is dark elemental, so I think you should be able to chain with TT's Quad Chaos Dark for some serious damage. Don't forget to dark imperil him.
You can't break his def/spr, but you CAN break his att/mag, so your Lid can help with that. He also likes to break your stats, so use Lid's Spec Guard on your DPS so you give him the full blast.
The dragon hit you can avoid by using CG Fina's AoE Reraise. Or ideally just make sure you beat him within 6 turns of him going super-saiyan. You could try to avoid it by not attacking him when it says "He's preparing for a counterattack", but that means you have avoid any unit with a auto-counter. I needed Willie so I couldn't do that.
If all else fails, don't worry about it. The staff is still WAY less powerful than the holy wand you get from the 10-mans. Let me know if you need any more help.
I haven't even started the story event LOL. I'll have to get on that as soon as the LNY event is over.