What if there weren't as many classes per realm?
What if every class had the same amount of surviveability and damage potential?
What if every realm had the same abilities at every other realm?
What if every realm had access to all of the same equipment?
You can make all of the right arguments that these are good and required things for a competitive PvP MMO.
Well, you know what else is important? Standing out. Being different. The market is flooded with WoW.
"We want to avoid the trinity" yeah you and every MMO in the world. To avoid the trinity is to homogenize the classes. And people are bored of that.
SO. To stand out, to not have boring homogenized classes (if there ARE classes), don't make them carbon copies. Don't homogenize them. Don't not diversify for the sake of balance, embrace the trinity its gonna happen anyways.
Otherwise... oh look another WoW that nobody will play and you waste a ton of time and money because wow players already have wow and wont subscribe to your game as well.
You HAVE to be different. Very, very different.
Also keep in mind that even after 10 years people still talk about the good parts of DAoC. It is worth impersonating, as even if you think their class diversity was a weakness, it will go down in history as one of the bests and is still around today. Which is more than you'll be able to say about TES online if you try to 'improve' upon it too much and your game ends up the same as everyone else's.
I repeat, if The Correct way of making an MMO means the game is perfect from a design and balance standpoint and that is the norm and what is expected, then to stand you want to make an MMO that is NOT perfect design and balance. Make it cool and memorable at the sake of balance.