Other folks have covered the bases quite nicely. Your playstyle as a BW will depend a lot on the situation. During sieges, BWs are great at piling on AOE damage. In open RvR you are a lot more vulnerable and will need quite a bit of situational awareness if you want to survive, especially when pugging. In scenarios BW/Sorc have among the highest variability in terms of impact. If the enemy focuses you, you are very likely going to die a lot unless you have really fantastic healers. Even then you will die your fair share. If for some reason the enemy does not focus you, however, you can absolutely demolish scenarios. I've seen BWs (and sorcs) completely carry their team damagewise when left unmolested.
Also, a little history lesson. Bright Wizards were initially one of the most overpowered classes in the history of MMOs mainly due to the fact that they have excellent AOEs and those AOEs did not initially have a limit to the number of targets they hit. Fortress defense was hilarious. You'd have a line of tanks blocking the stairs and a backline of BWs just raining death on everything. You'd often have a minutes long backlog of kill notifications. Eventually this was patched, thank goodness.
This hardly matters now, but BWs are excellent PvE DPS for dungeons. That said, BWs are HORRIBLE at solo PvE. The downtime is just mind-shatteringly bad compared to other classes.