It's one of the times FFXIV is borrowing from other large scale multiplayer games like TF2, which is a good thing and they should be doing more of it to improve PvP.

With how different the maps are, jobs are, the way jobs can impact team composition more than role, mean you should be able to adjust based on what you have. SAM for example adds to the general bulk of your composition more than the other melee do. There's also advantages that are more by job than role; selecting RDM in FL can offer lockdown for your alliance if there is an absence in warriors. There's just so much of a range of what the jobs are doing in PvP versus PvE. We can also just be able to shift to suit the needs of our team.

It's really a whole different beast from, say, dungeons in PvE, where there are more similarities between performance, what you can contribute, who is expected to take damage from what attacks, how much CC is allowed to matter, etc., and it's good FFXIV is making changes to suit the nature of large scale PvP. With Feast, I'd imagine it's different here in large part because the sensitivity of game balance is much higher here, and it's much, much, much easier if ranged DPS are compared to just other ranged DPS, rather than having to balance them to be 100% comparable to all the melee and all the tanks and all the healers.