Yes you can do it, the biggest problem is SE is rather unwilling to look at larger meta concerns with classes. They've just begun to look at other resource management but only touched on a few classes and not in a very deep way. Resource management is one way to make classes feel very different. SE basically just has MP and TP and more or less they function exactly the same. So they have one resource. I remember in swtor they had 4 management systems. One was a standard mana bar, one had two types of skills resource builders and resource spenders, one had an ammo system, and one had a system where it was like a mana bar but it would regen faster the higher it was. So if you dumped it all it was slow to regen, but you had skills that could fill it on longer cooldowns so there were times you wanted to dump the bar and times you wanted to be careful not to dip too low.

Now that's not the end all be all but that right there shows you systems that SE is just ignoring. What about larger meta concerns, well lets take the rdm, blm example from the first page here. Why is a rdm not punished so harshly by mechanics? Well because they have a means of dealing with mechanics, namely mobility. Now it's certainly an identity for a blm to be largely immobile, they want their feet planted in the same spot as long as possible. Here's the problem with a situation where rdm and blm do the same dps, dps is not the only concern in balance, the whole package is. Rdm was given something in addition to it's dps which thus throws the situation out of balance. So what do you do with blm? More damage, well that's not really fair? Mobility? That's boring and homogenizing. What about skills to deal with mechanics? Imaging if blm was given something like a blink spell. Wrapped in FF lore, the spell phases the blm into the ethereal plane(or perhaps the void) and while there are untouchable by material beings or abilities while still being able to affect them. Self only, lasts for say 2 - 5 seconds whatever is considered balanced, and has some cooldown. Now when something comes along requiring movement the blm can simply blink out and not get hit by the aoe or other mechanic. Obviously we can't have them blinking every single last mechanic away but I think you should get the idea.

As with the given mnk, mch example, and my rdm, blm one there are lots of things they can do to preserve a class identity, give them interesting ways of accomplishing their goal, all while doing similar dps. The problem is SE seems to now largely lack creativity when it comes to this stuff.