One of the reasons WoW had 14 million subscribers

[Calypsx]

They should just not label them instant then, because they well, aren't.
If they had cast times listed instead I'd be fine, but I expect something saying instant to be well... instant.

So if they had cast times listed instead would this "issue" vanish for everyone?

Though it's easier if the player base just learns for themselves because changing "instant" to "cast time" isn't going to change a single thing and the attack will still come out at the same speed it always has. Just now you'll have a fancy cast time label on them.

Animation times take a factor in how the game plays out. To inform players of that they should add that to the help section in game if it is causing confusion or an issue for players.