Rondo of Swords: Just went on the Good Good Path. (you get two choices, so you can go Good->Bad Ending, or Good->Good Ending.)
Anyway, allow me to re-illustrate how awful Marie's durability is!! Of course, I have Steadfast, Rook, Invoke Life whenever possible so a stat topic may be nicer to her. (although I'd take steadfast, rook and invoke life in the stats because it's a no-brainer to use them!!)
My party:
Altrius, level 39 Arch Paladin, 375 HP, 53+44 Def, 44 Mag. (Mag doubles as Magic Defence I think)
Selmer, level 40 Warlock, 177 HP, 32+31 Def, 69+15 Mag. This is a Mage, fyi, just like...
Galahad, level 38 High Priest, 185 HP, 22 Def, 68+5 Mag.
Marie, level 39 Divine Maiden, 114 HP, 15 Def, 65+7 Mag. Welcome to awesome HP.
Alhambra, level 39 Treasure Hunter, 458 HP, 38+12 Def. 34 Mag.
Ansom, level 38 Sniper, 448 HP, 37+18 Def, 13 Mag.
Party averages: 292,83 HP, 50,33 Def, 53,33 Mag.
So Marie has ~0.40 of my party's HP. And... that's even leaving everyone else out of the equation, all of whom have higher HP and Def than she does. Um. ~0.29 Def, which is... the def stat is pretty noticable. F'rinstance, Altrius suffers 50~70 damage from an attack, whereas Selmer suffers somewhere around 140~160. Marie is always OHKO'd. Of course, Altrius and Selmer have def up items, so I'd knock off a few points from the def but I don't think that salvages her HP. Yulie'd look like an awesome tank next to Marie, who also has NOTHING TO BOOST HER DEF! Mdef, yes, but def? No. Of course she has the awesome MP Regen (massive!!) with Martyr (gives MP to others) combo, which helps out a lot since most mages don't restore MP (Selmer's is lategame) while they have massive MP costs. Notably Galahad's 88 MP Abyss Gate (WITH MP REDUCTION!) running off a 200 MP pool.
I don't even use the tankier guys (Simon, Margus, Kay, Owl, Yumiluna), although Selmer is probably a top-tier Mage with regards to defense and HP: he gets Steadfast and Invoke Life, although this does not put him ahead of Galahad with HP. Probably also because neither of the skills is maxed, but still.
Cotton and Selmer are godlike mages. Selmer's Serdna Prison is a wide-area spell that... pretty much either OHKOs or puts things within an inch of their life. Due to Terah Spell he recovers his MP as well, meaning I use him to soften up the targets and then make Alhambra use her godly 12 move to finish things off. I mean, seriously, I read a guide that says Selmer is a worthless Mage, but he's my best! Galahad beats him only at range (and only 1 range at that!).
Cotton is awesome because she even OHKOs bosses, who typically are pretty durable. (plot boss: level 35, 401 HP, 72+19 Def, 70 Mag) Faerie Fire is excellent crowd control albeit with short range, and Dragon Fire is just murder. She's also suspiciously durable due to evasion and a good chance to survive with 1 HP. I'd use her more but she makes the game criminally easy, since her Overburst skill also replenishes her HP/MP, and charges to max after one casting of Faerie Fire/Dragon Fire. Having 8 move on a mage is just icing on the cake. (typically characters have around 5-6 move, with Selmer having 4, Elmer has 5, Galahad has 5, Serdic/Altrius has 6, Alhambra is a silly outlier with 8 and boosts to 12 with Sprint)
My only regret is missing Izuna for super cameo plus plus, but what can you do. Probably on a new game+ with EVIL ROUTE!