Don't misunderstand; I am not saying one is impossible, wouldn't work, or even shouldn't be added... I am just saying we don't need one. Another healing class or tank class will always benefit World of Warcraft as a whole, but a pure DPS class is just going to saturate queues negatively. In a perfect world, all new classes will have the option of tanking or healing, but that's not to say it's necessary nor that the world is perfect.
I'm just responding to the comment that "this class is exactly what WoW needs!" and I'm disagreeing on principle.
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Sorry if my response was a little bit over the top there, thanks for the open minded reply. I agree with a lot of what you are saying. Dark Ranger ultimately is something that can work, it's not my primary choice but it's up there in terms of potential classes that could be added to this game and not simply exist by leeching abilities off other classes. It's a unique class and there is enough appeal that it could work.
I'm still strongly towards tinkers being added next, but I think the next hero class could absolutely be dark/void rangers. In the meantime though, we should consider how we can make it a more varied class with the potential of tanking and/or healing.