I stopped playing D&D Online awhile back because of its lack of a decent PvP experience and the game sites that I go to show that the game gets voted down against other games mostly due to the lack of PvP while it wins pretty much hands down in PvE adventures.
D&D Online is pretty much unique and fun and has the feal of the pen and paper game as everything is dungeoned out and instanced, and that should not change for PvP as that is what makes D&D Online unique.
But what I think D&D Online could and should do is to start creating instanced PvP dungeons. One instanced dungeon could be set up to allow a lot of players to enter at the same time and then have a last man standing conclusion. Another could be set with tons of moveable walls and traps that players could move about to trap each other in mazes and ambush. Another could have many cages of prisoners and be a two verses two team thing where players try to free the most prisoners they can of their asigned colors before time runs out. I mean there are all sorts of instanced dungeon PvP type scenarios that D&D Online could create without losing the flavor and feel that it currently has, and some PvP dungeons can favor certain classes more than others. What this would mean is that there would be no best PvP class as each PvP dungeon would likely need or favor different characters. If you are trying to free slaves you either need to take a lot of time looking for a key or get someone who can pick or open a lock to the area and finding secret doors and passages can also save ample time.
I would like to see PvP brought more into the game, but all PvP should be in their own customized dungeons.