Hmm, looks like a coinflip as to if Titania can successfully kill Marle in one double. Close match. Coin-flip resolve: If Titania fails to kill her, then Marle Provokes, which... means she has a pathetic damage giggling Titania physical incoming, which just might be enough to kill the 3 HP Marle. It'd be funny, at least. (Plus, FE has no damage variance in attacks, so Marle can't heal until Titania does badly on an attack.)
As for the TB speed debate...
Of course is your average DLer voted that way (that turn-based characters could never be doubled), Ghaleon would be unrankably powerful. So hey.
Ghaleon is almost unrankably powerful (though not as bad as Zophar?), but I suppose there has to be somebody at the top. Anyway, to be precise, the issue is when
both characters are turn-based - nobody will argue that Tidus shouldn't double Ghaleon like mad, because Tidus is a fast character from a CTB system where that speed actually does double in-game. Nash, however, never actually doubles, so his speed isn't as good as it seems from a strict percentage basis (or Alena, or Aika, etc.). Basically, the speed stats aren't directly comparable. For turn-based characters, it's more like initiative each round, while for CTB characters it's total number of rounds taken.
There's a point to be had that fast/slow TB speed should still be rewarded (though... with first strike as important as it is in the DL, I'd say it generally already is), and additionally allowing TB characters to eventually double each other can break up some stalls in long matches which (correctly) will punish slow healers. So... my personal preference is to let the TB speed still work as is for initiative, but to average that speed with 100% as far as gaining doubles goes (so 110% avg. speed -> 105% avg. speed, and 140%->120%, though only for getting extra turns - the turns they do get are at their normal TB speeds). Also to cap the max turn-based speed at 120%, and the minimum at 80% (=speed faster than 140% is ignored because you're going first, we get it). Arguably it should be even tighter than that - with those caps, Piastol (infinite TB speed) still exactly 3:2s Ghaleon, which just feels odd.
Anyway! That all said. Um, yeah, Ghaleon should slaughter FA here - better durability, CS to absorb an attack. FA isn't even that fast normally anyway, and I certainly don't let FA spam her good damage move (I don't let Ghaleon spam CS or his other options either, but his damage is pretty consistent so it doesn't matter much). I do look for any excuse to vote against Ghaleon I can, and I suppose from a flavor standpoint we could force Ghaleon into his Lunar2 form? Hmm.... assuming the no-magic fight is illegal, seems like FA might win that one. Though not if both of them are on AI (since her damage is far less consistent). Yeah, sticking to a Ghaleon vote.