It's definitely super weird how the melee combo just doesn't work with some of the mechanics expected strategies, Caster Baiting Manta while bursting down the first pack of Adds before first Jabberwock doesn't feel the greatest on RDM because at best you can single target hit the manta and dump the AoE finishers on the adds to help BUT... If the adds don't die, you have to skip out on Moulinet again which will lower your overall AoE damage and thus cause the face to take longer. It's super weird and, RDM likely wasn't considered when the Strat was made or the mechanic was designed.
Another case is when the party is split in lava phase of m2s, Don't expect to melee combo at all until that entire phase is done, this going to make faster rdm kills a pain when rdms want to dump resources before the boss dies. it's less of an issue for Prog when gear is low but will become obnoxious as things start to die faster
Ride the Waves in p1 has 2 strats both of which force your rdm away from the boss especially if you're trying to give the melee uptime for the mechanic
The penultimate burst phase in brute abominator also gets tricky because you have to be at the wall and you can only hit the spawning add for a little while before the tank pulls it away to do the quarry swamp portion of that mechanic which of course means you're not getting 2 Melee combos in the burst window on that front.
I hate to say it but i think Red Mage needs a second Melee combo thats ranged based so that this stops being an issue, Like the Redoublement combo can get buffed if you do this ranged combo prior and the idea is to alternate between the 2 combos. At least with this, Red mage will always have the ability to do it's core loop without completely stalling it's rotation and shifting it out of burst. think of it as a "Storm's path" combo and Storm's Eye combo that the job swaps between for max potency