I've been playing Neverwinter MMO yesterday and I'm liking it a lot. I'm currently playing tank and it's very satisfying. You have a guard meter when you block attacks, block too much and you can't block anymore, you can assign traits and skills that will replenish that meter (think of it as if it was mana being refreshed or something, don't block and it goes back up naturally). You have a lot of threat gaining abilities which can make it hard for a good tank to let things get too out of control. I don't know how the other classes play but I'm loving Guardian.
http://youtu.be/8QK1eK6Z43I Guardian video
http://youtu.be/KDiFet0v05s Boss dragon fight. I saw some people fighting this yesterday so I looked this one up specifically.