Deadwing wrote:
If you care about drop rates:
RDM+THF is the only answer
If one of you has or levels a dual box TH, or you're interested in doing mercenary work where the drop rates are high (or the people you're working with have TH):
NIN+RDM isn't terrible by any means, but RDM/NINx2 is going to be better in every case I can think of. The ninja is going to spend enough time casting ninjutsu that dividing the tanking among two rdms is going to put their melee potential close to 1 tanking nin, if not higher. You also get 5mp/tick more of refresh, a second large mp pool for chainspell nuking, a second person to enfeeble etc. There isn't much in this game two really good rdm/nin's can't duo; Byakko/Cerberus/Khim/Seiryu are all possibilities. Even with mid-range gear you can quite feasibly duo things like Jailer of Faith, Mother Globe, Suzaku, Ix drk, Roc/Simurgh, limbus floors etc.
The only other thing I can think of that you might want to go is BLMx2. It's got good sea/limbus farming potential, can still hack it against a lot of NMs. I imagine you'd be in higher demand by endgame LS's and BCNM groups than thf+rdm.
I must be way out of the loop if rdm/nin x2 can duo cerb and khim now.