I disagree with some points. The tanks are better served staying tank to do world quests, you can chain pull mass groups and be done much quicker than most dps classes (My knowledge on this is only as far as a blood dk from beta testing them). As far as healers, i've found that there's no shortage of squishy dps that wouldn't mind having a healer with them, and you're much better served focusing only on your MS until you get to around level 6 artifact knowledge (might be 5, can't remember 100%). As far as average raiders, it's hard for me to see through their eyes since I plan on pushing it to the limit as best as I can in the 4 weeks I have till Mythic releases, so you may have a point there
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Um, no. Top raiders are going to be required to be as far progressed as possible. My guild is in the tail end of top 200 us and we're required to be as prepared as possible, and raid spots will be given out accordingly. I'd assume the majority of guilds ahead of us are doing the same, and it will be important to have as many traits as possible for pushing content early on.