You can't really use "BLM is better at X fight in a tier, therefore SMN is okay!" as an argument as a static isn't likely to have the perfect roles for every right, forcing people to change jobs every step of the way. You're not going to have someone be a MNK for O6s then be NIN in O7s because it's more efficient because aside from expecting a person to be able to play both jobs with equal levels of proficiency, you also have to take into consideration gear progression.

As a result, most groups I've ran into aren't using RDM or BLM for a caster slot because SMN outshines them in the big picture. So that's either a failing or the raid tier giving each job a chance to really shine so that taking any caster job is viable for a raid static, or it's a problem with the jobs being imbalanced, and in my opinion, it's probably a little of both, especially when comparing RDM to SMN.

The utility and mobility packages of the two jobs are comparable, with most of the time SMN having better utility, and RDM having arguably better, though only in short bursts, mobility. As such the two jobs should be outputting damage much closer to each other than they actually are. SMN might be slightly over turned at the moment, and RDM definitely needs a buff (I think the devs over valued the utility benefits of Vercure and Verraise) OR RDM needs better mana management to make that utility viable... or both.