I would like, after a lot of experience playing games of this gender, to writte down some ideas I think are really important for an MMORPG:
1-From my point of view, the most important aspect of an mmorpg is the social part, so it is crucial not only implement aspects like guilds, parties, trade...but also "force" players to socialize. When you have the option of doing something with other people, social aspect of the game becomes optional, you can do or not; but the true social part of an mmorpg is created when you NEED other players to continue your adventure. So, I think is a bad idea adding options like group finders, dual specs...because those limitations force you to meet another people for doing some quests, make that being a healer or a tank provides you some reputation among people in your server, etc. If everyone can do everything or you do not need to socialize for a dungeon I think one of the most important moments of socialization in game disappear.
2-Other crucial thing of and mmorpg is immersion and one thing that I always loved are the classquests. I think that breaks the RPG aspect of a game when you are a hunter and when you create you character you alredy have a pet. I think class quests, and difficult class quests, are something very special from an mmorpg and I have always loved that way of making you connect with your class and your future. Create an excelent narrative of each class making them unique, is something very important form my poing of view.
3- The value of money: other very important thing for the social aspect is creating a good economical system and make that money have an important role in the game. When in a mmorpg you have tons of money with no value, is another reason to not socialize. I think it could be good to introduce a AH system, make that vendors have good stuff (not very good but at least some weapon or part of armor useful to spend your money). That should be completed with a good crafting system and in fact, I like a lot that system that developers are creating of "hiring" another players. Very very interesting.
4- Personaly I am not a big fan of level auto scaled zones, because I think for a better immersion of the game and the role aspect, zones should be more epic along the progress ¿does it make any sense to be a lvl 5 fighting agains dragons in the most epic zone being helped with lvl 45 people and at lvl 30 going to kill some wolves in the forest near a city? I think zones along your progression, should be more spectacular and epic. I have tested the auto scale zones in some mmorpgs and it kills my ambition to go to some special zone or very rare area because, at the end of the day I do not have to work for going there, I can go whenever I want. And thats not epic.
5- I am also not a big fan of transmogs because I think it rest some social value to the equipment. Maybe for not very rare or legendary items I could work but I think special items should have their unique skin.
6- I personally like the distinction between pvp servers and pve servers. Indoubtely one of the most legendary moments of World of warcraft was the open field war agains horde and alliance in stronglethonr valley. Everyone have enjoyed and suffered it and those moments are in everyones heart. With an unhororable system of reputation for pvp, I think PVP servers are the key for an mmorpg.
7-I am not a big fan of how factions are designed. I think there should not be an evil and a good faction, but instead, two different way of lives, cultures, values...I remember when I played SWTOR that being a sith was so frustrating because you could not chose to be a machiavellian character or something different, you had to be 100% bad and torture, kill, poison people...and if you were a jedi you were going to be always good. I think thats not a good point to empathize with your faction, your quests...every race should have their point of view of life, not just being "good" or "bad".
8- There some other important things other people have writte down like boss mechanics, combat system, pets...but the last important thing I would like to say is: please please, try to create a system to balance the factions. Do not allow like in WOW that one faction controls almost everything because that is really boring and the more balance the more fun for world PVP, arenas, battlegrounds...
I love when developers and gamers are in touch and we together can create an mmorpg. Keep working this way!!
I agree with everything.
About scaling, it won't be like in Guild Wars 2, when you get to level 10 everything will be harder in that zone, when you get to 20 it gets even harder, every 10 levels the bosses and dungeons become harder as well, but more rewarding of course. The bosses add new skills and mechanics, etc.