I'm of this opinion, generally.
Some jobs are just better than others, its just in the nature of competitive games with different characters/archetypes that have differing mechanics or skillsets. But aside from day 1 of the entire PvP rework and through a couple "balance" adjustments, I just don't find any 1 particular job to be glaringly bad or "overpowered;" the exception being SCH, which simply put is either going to vary between amazing or useless, depending on the basic competency of their other 4 teammates.
However, where things start to get a little bit more complicated comes from the random team compositions. Some jobs just synergize well with others. The big issue I see is the possibility of lopsided compositions- and I don't necessarily mean tank, healer and dps distribution complaints we saw early on, though this is similar. A team of say, DRK AST MNK DRG BLM is going to have an easier time than say, a PLD SGE NIN DNC BRD team if they both have equal skill. The melee vs ranged problem for DPS can lead to very one-sided situations like one team has 3-4 noticeably tankier melee jobs all diving-in on squishier jobs that are forced to engage without cover. All of the jobs may be viable, but that's usually in a sense if they exist in a vacuum.
I once saw a good comment on reddit that I wish I could find again about Crystalline Conflict and an accurate, alternate take on the jobs and their "actual" roles; like there being "Executioner" jobs (like MCH or NIN I guess), "Pressure, Support, Interference, Set-up, etc." (I can't remember all of the categories used, but you get the gist of it). But if you get matched on a team that runs heavily on Support or Interference, killing targets becomes more difficult and you basically can only win by essentially majorly outplaying a better-stacked team.
This doesn't make any 1 job bad, but if they're in a particular match-up where they're not allowed to perform how they're intended to (ranged jobs seem particularly susceptible to this), they'll get picked-off or be unable to fully utilize their skillset. Like if your only melee is a NIN against a team that has 2 different melee + a tank, direct confrontations will never end well for your team.