I’ve tried to find it before in the old blue tracker archives, but devs posted an insane amount compared to now, so I haven’t been able to locate it.
Back in wrath they did do a small buff to frost mages at some point if I recall correctly, and made a post basically saying “we don’t plan to make it just as good as fire because it would be a problem in pvp, but it could be a bit closer”
Just can’t find the actual post.
At the class level, they were, not at the spec level.