Its difficult to say really since many skills have unknown numbers attached. For example piercing attack migh be straight up better than royal moon blah blah depending on how muh pierces and such. I also dont know how much last fortress buffs by, could go on. I think maribel's ability to see boundries might be #1 though, and i feel majesty is in fact far better than byakuren's buffs. I mean having them all together owns yes, and byakuren being able to transfer them to others is great to, but in of themself, if i could have majesty or one of those buffs on other characters, id take majesty. Note though that the mag or atk buff might be a better choice for pure glass cannons like flan or whatever but that again is dependant on the character.
So i just beat hina in my current game and boy was it messy. Most of my cast cant help but apply some kinda debuff with their attacks but remi and niroti, but both were pretty weak to fire so i couldnt have em out for very long, particularly cuz that was te spell hina decided to toss at me like 2/3 of the time for te entire fight. I accidently silenced her with parsee by using small box (argh), then she buffed herself. So i whilped out byakuren to use her big spirit nuke, thinking the debuff wouldnt matter cuz hina already had buffs to "block" the debuffs. But it turns out that one of the stats ended up debuffed just a bit again, so hina buffed again (didnt reverse it, treated it like silence or terror or something and buffed all again instead). Argh. I beat her first try but it was really effing messy.
Incidently kraken wasnt too bad but it killed my china before i could even move a single character. Nuked her for like 400 twice before my first move, qq. Killed dem 8 eye serpent foes too, though the first stone of awakening was behind the 2nd, doh. Tried to get a 50 retreat achievement too but ran out of tp at escape #47 doh. I could have calculated it in advance but it was more like i ran twice anyway to scrag a foe at full everything and was like might as well put my 2 runs to use. Didnt work out though. Having a meteor drive will be nice for tenshi though.