If delta rank played a part in XI, it was modest to the point where a decent number of people say your level has no effect on performance at all.
In XIV, level completely dominates every outcome in all the disciplines. Almost no other parameter significantly affects any relevant outcome parameter like HQ rate, successful synth completion rate, sp per hour. They only have very minimal effects on sub-outcomes like accuracy %, damage, completion progress, quality gain, etc. Those outcomes don't actually matter if they aren't that relevant. 45 damage really isn't better than 38 damage if it doesn't unlock higher SP/hour.
Did you mean to say a R50 with minimum INT will outperform a R35 with max int? Heck, a R40 with INT 50 will probably outperform a R37 with maximum INT. A Naked R40 smith beats a fully geared R37, that's for sure.
Once you hit level 50, almost no character progression you devote to will make that much of a difference. Even the difference between Jade Crook and Jade Crook+3 on a R50 conjurer really won't unlock any significant outcomes for you. Your nukes will functionally perform about the same.
The stat and attribute system in XIV is probably the most placebo-heavy RPG system I've ever seen. It's as if they thought we wouldn't notice the stats did anything, and continue merrily getting them as if they did. It certainly makes balancing the game easy when the stats don't really do anything valid.