Define depth or difficulty in general? You'll have a lot of people that say BLM is extremely simplistic and has very little depth to, especially with all the QoL changes it has had and you'll equally get people who say its too difficult to play.
Which one do you listen to? Who decides said class should be better than others on merit of difficulty alone? BLM is designed to be top because it lacks raid utility and it only brings raw dps which is exactly how it should be. How difficult or easy BLM is to play should have no bearing on its DPS balance.
The problem with reaper is that its overtuned for how much utility it has. Its pushing out too much dps regardless of player skill. It could be the most difficult job in the game and I'd still be calling for it to be nerfed. If its gonna be doing DPS on the level of SAM and BLM then it needs to lose its utility, otherwise its DPS needs to drop down.
Don't be ridiculous. Ease of use has nothing to do with their lower DPS and has everything to do with game balance in uptime. DNC is a support close and BRD/MCH basically have 100% uptime during mechanics with the only exception obviously being when the boss leaves the stage. You can't have that kind of uptime and have high DPS. Its why I wasn't surprised at all when I saw SMN numbers. I KNEW they would be in the the physical ranged area of DPS before EW came out. That said, I think SMN is underperforming and needs a buff, but don't expect it to significantly outperform ranged physical jobs since SMN is essentially completely all instant casts now.
I wasn't making a comparison, just using it as an example of why I don't consider difficulty a valid reason for balance. One of my friends for example cannot do Akira's 1F knee. Meanwhile I can fire it off over and over again with zero issues. "Difficulty" is subjective. I find doing his 1F knee to be quite easy to do and I don't believe he should be as strong as he is in VF5FS just because he has 2 or 3 "difficult" moves, one of which you can ignore and still compete just fine with the character.
Obviously MMO's are different, especially being mostly PvE, but my point was I think balancing around ease or use or not is dumb. Should a class that's slightly more complicated be more rewarding? Sure. NIN imo should be a little better than it is right now. Should that be the defining reason? Absolutely not. RPR is 100% overperforming, but I don't agree with the idea that it should have the lowest melee dps just because its "easy" to play. Its DPS range should be in line with the rest of the melee DPS that have raid utility.
As far as I'm concerned, a well balanced MMO would lead to exactly that. You play a class because of its aesthetics, not because it outclasses everyone else.
That has nothing to do with difficulty and everything to do with game design and balance. As I said to someone else, you can't have that level of uptime and high dps. Regardless of how easy RPR is, they are still a melee class that has to lose uptime to mechanics unliked ranged classes.