/WAR is pretty much the only way to go for exp.
/DRG has been parsed and proven to do slightly more damage over time than /WAR has, but this is because of jumps, and a slightly higher accuracy. (at least that's what the parsings said from the live journal I read).
The following link has some weird shit detailed for anyone interested in experimenting with MNK and what it can sub.
http://users.livejournal.com/_remus/
Personally Miewn, I kinda agree with most of the other people here on MNK/WAR and some of the other SJ's.
MNK/DRK would die too fast, one weapon skill with Soul Eater and you can kiss your ass goodbye. Interesting way to try and steal hate to level guard, and piss your party the hell off though. :d
MNK/THF in KRT is kinda like taking a THF/MNK to KRT with high level knuckles and everything. It just doesn't really work the same as a MNK/WAR. . . sure you might be getting some ups to WS damage, but you're probably not keeping up with the other MNKs using /WAR and getting double attacks in.
If you're going for farming, I have two observations. MNK/WAR you'll be able to have more claimability on mobs, as well as be able to kill the mob way faster than MNK/THF. MNK/THF is kinda useful cause you still have chi-blast to claim, (which is a 3 min timer btw) and you're able to steal/mug things if you get close enough. Also you have flee on your side to help you get around faster.

Treasure Hunter from /THF is kind of moot in my opinion, considering alot of the time I've farmed without it and gotten better drops faster than I have with /THF, so that's up to you. Personally since you have THF leveled, I wouldn't be too concerned with farming with MNK.
Oh, one other merit of /WHM I've noticed no one added. It'll help when you're skilling guard, because you'll actually be able to CURE bomb yourself instead of healing for 10-15 minutes.
Personally I haven't played around with MNK/SAM MNK/NIN MNK/WHM MNK/DRG and the ever odd MNK/BLM lol. Though I'm pretty sure the last one you probably should avoid unless you're just really really really bored. and wanna get a kick outta screwing around with it. MNK/RDM hundred fists with en-spells would be kinda funny imo.
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