Both SMN and MNK have had a renaissance of sorts in the last few years. SMNs figured out a nice loophole for earning 20-40Kexp/hour, and SE has indicated they're fine with it. SMNs are also amazingly useful for endgame fights such as Odin, whereas BLMs are useless. MNKs turned out to be fantastic tanks for Salvage; since the nature of event involves fighting without any weapon at all for the first few minutes, and since they can do considerable damage while still tanking effectively as /NIN, they (along with SAM) earn the choice DD slot for low-man Salvage.
Gods are still gods, sea is still sea, but with the variety of endgame activities available, you can certainly find an endgame shell that would be glad to bring a MNK and SMN onboard. (We've been playing with the Odin 2 hour summon, and someone popped off a crazy 7K+ Zanzetsuken against Jailor of Love last weekend.)