I don't have a problem with it being "easy"/"simple". That's fine; some jobs can be more complex and some can be easier. I don't think balance should necessarily be done with simplicity as a factor. Being easy just means the skill ceiling is lower than other classes and it'll be easier to play the class at a high level.

The problem I feel is that even at the top level, where everyone is playing each class at near max capability, RDM is just better than the other two casters. They do more damage in fights while having more utility & mobility. They're also the DPS with the least punishment. DPS should be balanced (as Yoshi himself brought up) partly by their susceptibility to mechanics. Being less punishing, RDM DPS is much less effected by mechanics than BLM or SMN. BLM can lose Astral Fire/Enochian/Foul stack from moving for more than a second, or lose a Fire IV; positioning to maximize casts is necessary. SMN needs to optimize all their CDs and Bahamuts to each fight differently.