BLM is the mobile caster now.
Well, BLM is the one I don't play. And while i get that they have teleports to and from their lines, don't they still need to cast basically all skills?

And what is the reduced mobility is SMN compared to previous SMN?
Just the increased difference between ruin2 and 3? Because if that's it, with more ruin4 procs, two trances, the need to interweave oGCDs and to make sure you get the wyrmwaves all make you not need to stop and cast ruin3 that often. Even against a dummy, I at least, do more dmg if I don't try too hard to use ruin3.