Current team: Brahma, Mammon, Raiko, Thor
Bench warmer SSRs: Justitia, Tyr
Simply put, I am a full Thunder baka because I just find it so much fun to play. Namely, playing with Phantom Elemental Lord Thor. I also find Brahma great fun to play with, since despite being unreliable, she's out of this world when things line up right. Raiko is an amazing backbone for any party, so I don't want to part with her either.
Minmax reasons would drop Thor, sure, but for me, Mammon is the only replaceable because of FUN reasons. And the only real replacement for her would be SSR Baal. And because she doesn't seem fun at all to play with (90s debuff? You might increase Thor's chances even more, but fuck off), I'm not really very interested in spending the MT for Thunder.
I guess I should mention that in theory I'd be interested in Marduk, due to being an overall powerhouse. Still, with Thor in the party, she'd be rough to fit in. There's also Athena, who has her (strong) niche uses and most importantly, I like to spend my bricks on Thunder weapons, and her FLB is just nuts. And last, but certainly not least, none of my teams have a fucking healer (Light doesn't count, more about that later). As such, Dian would allow me to do content where being defensive would be ideal. That's not ever ideal, but uh, I do like to play defensive teams because it is fun. And I simply can't at the moment.