I'm glad GW2 doesn't have mod support. Even though I'd love some mods, like things for improving crafting and the auction house, I'm glad there isn't room for things like DBM to appear. In the MMO trinity thread, people are talking about how "epic" the Kael'Thas fight in the Eye raid was. I remember that raid. My guild did it, first time, no wipes, with pretty inexperienced raiders - because we just did what DBM told us to do. You just follow the prompts and instructions, no real effort required other than skill-checks for how well you can do what you need to do, when called upon.
DBM really kind of ruined raiding, since you had to have it installed or raid groups wouldn't take you, but if you had it the game became quite boring. I think WildStar, with it's UI mod support, may end up going the same route - everyone needing to install "raid-critical" mods, like threat meters, heal meters, and deadly-boss-mods style mods. Not a fan.