"Frost is fine, it's the top PvE 5 man dps spec [and] I have yet to see arcane mages sit at 5k dps consistantly through a random heroic."

5s are too variable to be a good measure IMO. Buffs change, tanks pull half the instance or two mobs at a time. Bosses don't live long enough for procs to even out.
All specs are fine for them. Though if you're not seeing mages of all specs over 5k (way over) you're getting consistently weak groups full of just-turned-80s.

"You need to realise every spec needs to have strengths and weaknesses. You can't have the spec that offers the best utility with freezing, chilled and iced to also be at the same single target dmg as fire or arcane."

Why not?

Not that the question matters: the other specs have as good or better utility/features while also doing better single target DPS. Frost frequently ends up bringing nothing to a raid except ice barrier, extra ice block, and sub par DPS.

I love frost but it's not even my go-to leveling spec these days. This makes me sad.

PS Frost is not the best AoE DPS spec.