Tried Trifruit this morning as well, went in with Valk, Siren, Angelion, Shynee, L/L Venus, friend Valk.
Got all the way to the Tamadra alone and screwed up a stall, ended up cascading in to enough damage to kill it 4 turns before Shynee was up. Left dungeon because wasn't going to drop multiple stones at boss. Itfeltlike it was going to be easy enough, or at least didn't feel that difficult. It all hinges around how many light orbs you get in the first round to sweep the seeds and then burn the fruit. With max skill Valk, Siren, Angelion, and friend Valk you have pretty much on demand light orbs for round 2 and 3.
So went back in with friend LTron, thinking hey an extra .5 multiplier should be fine, I can heal up on round 3 before they attack, no problem. Didn't make it past dragon fruit. Will try again later today after King Carnival. (which I just checked is at 12am CST for me so it looks like I'll be burning a stone to get that started, bastards)
Maybe could replace Siren with my second Valk but wanted the extra orb changer. Don't think I have any other light orb changers that are Healer.