It doesn’t need to be the “go to” mage spec for anything. It just needs to be acceptable.
For hardcore players trying to push difficult content, it’s almost irrelevant what specs are the strongest and weakest. A lot of them will be playing those strong specs. RWF and MDI players don’t tend to stick with just one spec (at least as far as I can tell - but I will happily rescind that comment if someone has the data that I’m too lazy to collect). Exceptions to that rule are likely specs that are constantly strong or impactful in those settings.
But a lot of us “average Joe” players don’t swap as often (please note that I said “a lot” and not " a majority"). Some of us have a class or a spec that we’re really locked into, regardless of their performance. Because that’s what we enjoy playing. I’d be willing to bet that a good majority of the players who’ve been complaining about the state of arcane don’t care if it’s the best, as long as it’s not behind by an egregious amount.
This week in our raid, there was a boss on normal (Sproketmonger) where I and our feral druid parsed the exact same number for our overall spec (not item level). Feral druids are approximately middle of the pack right now, and there are about twice as many parses for Feral as there are Arcane (so there’s obviously going to be some bias here). He did almost 24% more damage than I did. I’m sure someone with a stronger background in statistics can point out some flaws in my observations, but at the very least, it’s painful to know that I can parse in the 90s for a pull and still be 20% behind other players in terms of raw damage.
I don’t need Arcane to be the number 1 DPS spec. I’d be fine if it was still the worst of the mage specs across all forms of content. I just want it to not be more than 24% behind average. I don’t want to feel like I’m holding people back by choosing arcane. I want to be able to play what I enjoy, with the people I enjoy playing with, without feeling I’m the reason we aren’t progressing faster.
And I do fully expect to see some tunings soon. I’m expecting to get some raw percentage increases to spells / talents / tier, but no fundamental changes. Things that will course correct the damage problem, but nothing to fix the playstyle complaints.