Buttons =/= Abilities.
Feel free to make duplicates of every ability and alternate between which button you activate it by if you so please. It will not affect the complexity of your job in any way.
This was never suggested, as they are not functionally duplicates or "stages" of the same ability. Deathflare cannot be cast while not in Dreadwyrm Trance, nor can Dreadwyrm Trance by recast in the time that Deathflare is available. Likewise Enkindle Bahamut cannot be cast without Summon Bahamut first being activated, and Summon Bahamut cannot be recast in the time that Enkindle Bahamut is available.
For the most part, you're simply dealing with people who feel that, say, breaking up Ruin I into combo-cycles of otherwise identical abilities merely varying by 10 potency each as to take up 3 buttons to perform the same filler function (but at faint loss if you have to reapply DoTs just before its third stage) would be a meaningful increase to complexity worthy of its button bloat.
Your only actual, and easily countered, reason would be accidentally double-hits in regard to the suggested Dreadwyrm Trance <--> Deathflare pairing -- causing early accidental Deathflare casts -- which would benefit from the same QoL changes that would affect any such ability or ability toggle with a stacked Cancel Aura effect on the same key, such as Defiance, Deliverance, or Darkside. Simply put, just preventing the stacked action (just as Cancel Defiance is already a stacked action of Defiance, or the cancel aura of any other oGCD stance, and can share the benefits of such a fix) to be queued during the first's animation would be sufficient. That said, you could also go further as to create an iCD of whatever safety margin you see fit, for which margin of time after activating DWT, DF cannot be cast.
But, yeah, it's mostly the "Surely, more buttons means I'm playing a smarter game" meme.