Prepatch.
1000000% prepatch.
Frost was NOT overpowered in raids in beta. It was NOT overpowered in m+ in beta. It was NOT overpowered in arena in beta. The legendary nerfs brought the spec well in line. The spec would be limping along if it was only hit by the prepatch 10% lance nerf. Then blizzard dumped on it more with a blanket damage aura nerf. Lord knows why.
On prepatch, it was way strong because of azerite powers. There was - a lot - of complaining and so blizzard did what they always do. They ruined a spec for 2 years cus the losers who play this game can’t stand losing at dps in pointless content for a week or two.