what i love about DDO is the complexity and customisability - not graphical but functional - that we have to design our characters, and the relatively complex environment (ok, look, we have traps and puzzles, but that's two steps ahead of some other games) that we have to test them upon. classless or multi-class character system is a must, i do play pure-class toons in DDO, but not always. having ways to interact with your environment other than hitting it is a big thing for me - traps, secret/locked doors, puzzles, and even just levers/switches etc.
i also love the not standing still to attack or cast - big fan of that. i'm not fabulous at twitch but i prefer a game with it than one without. in fact, games must support strafing with WASD and default or toggleable mouselook, rather than "hold down something for mouselook." i'm not dealing with that, it makes my eyeballs itch.
i don't care about visual customisation. it's nice, but honestly i'll play a stick figure and like it if the mechanics of the game are good enough.
i don't care about payment method in itself, but i don't want to feel exploited - i won't play a game where i have to pay for "necessary" items etc. i'll pay monthly, or i'll buy content, or i'll spend on utilities and cosmetics and fluff, but if the core mechanics of the game involve my wallet, i won't play.
good customer service would be nice, but enough of a community to mean a decent wiki exists is more of a priority.
world building is a huge plus, but i can always go play minecraft when i want anyway, so it's not a must - it would exclude too many games if it was.
i have tried:
Neverwinter... good action, but very simplistic for "D&D". no multi-classing? purrr-lease.
TERA... i didn't get far enough in to experience the serious gameplay, but... i just didn't care. choice of race almost doesn't matter, gear is class-locked, kill ten rats, etc. crafting seemed ok though again, didn't get into it. honestly, i won't be going back.
Age of Conan... i might try this again, i liked the feel of it, but it felt a little clunky to play. i think it had "hold something down for mouselook" but i'm not sure.
Scarlet Blade... hahahahahahaaaaa oh gods - so bad it's good? ok, no, but bad enough to be funny for an hour or so with a friend. like TERA, a good example of the type of game i don't want to play. kill ten rats. woooo. ladies with bouncy cleavages can not cure all ills.
Warframe... hmmm. loved the random levels, liked the art. bit too grindy/expensive for what it was, and a little too fast for me. i guess my unreal tournament days are over lol. still, good group combat and interaction (sometimes, but hey, PUGs).
Starforge... too alpha to tell, haven't played much as a result. love the idea, but there's lots of game missing.
Ryzom... liked it, might play it some more, but i don't think it's what i'm looking for - again with the clunky.