Well given your stance on this I hope you complained equally about progressive nerfs to raids, flight paths, mounts, portals to major cities, etc. Because it is all about convenience. I trust you never use any of these things ever because if you do you are a hypocrite.
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There is a very big difference between scrapping specs and giving tri-spec. If I have tri-spec I can still only heal or dps or tank during any given encounter. If you scrap specs and give all abilities to a class at all times they can tank, heal and dps all at once. We're not asking to be able to everything at once, we're simply asking for the ability to freely switch between specs without having to hearth, retrain, set up bars and get summoned back. There is a big difference between the two.