For those of you who refuse to use mods, here is some food for thought:
Quote from: Drysc
"No, I think we assume that those who are working on the extreme endgame PvE content are going to be doing anything they can in order to help increase their chances for success. By both embracing the UI mod community and their addons, as well as assuming that players are going to be using them to great effect versus our encounters, we have to design encounters that assume their use or the encounter is trivialized by those on vent, those with a countdown, those with a threat meter, etc. Once a lot of the guess work is removed with mods we have to raise the complexity beyond what a mod can purely assist with. I think at this point we're forced to assume everyone is using mods to great effect versus our design complexity, which in turn forces everyone to use those mods. It's probably somewhat debatable what mods are required and where, but it's certain that we have to take them into account, lest the game be trivialized.
UI Mods have become an integral part of the game for many players, and we've been extremely pleased with the amount of customization and information they're able to provide. We're continually working to assess and implement new UI features, many of which have come straight from the community, to help ensure that the default UI is as full featured as possible while remaining uncluttered, clean, attractive, and easily approached."
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I think I can speak very surely when I say that Vashj is one of the more difficult encounters in the game, necessitating the use of mods. Heck... Morogrim, Lurker, Leo... all of them would be much much harder without them, and would test even more that patience of casuals with limited raid time.