Finally cleared the new trial. I tried to sneak Valentus' Ramza to the last boss a few times, but I couldn't get past those damn bombs with just two mages in the party.
In the end I loaned Bonkeng's (alt) Lightning, that Ice Blitz for the bombs makes for a huge difference.
The team I used was Cecil, Agrias, Lenna, Tellah and Kefka. I know people tell you to stack mages, but I don't think I could've done the last boss without Cheer. His normal attacks hit really hard even with Cheer on, and if he hits a mage, he can crit for a 2k. Remember to land a debuff on him every turn, doesn't matter what it is - deprotect, deshell, anything works - he'll waste one turn casting Dark Wave and clearing it off.