It last 1 second.
PvP is a dead part of wow, those talents should be apart of the talent tree for those that want to play PvP. Melee has literally no reason to slow something unless they are running away - how often does that happen in PvE.
Frostshock is useful for elemental, they are ranged. Chains of Ice does a lot of damage. Harpoon = PvP, useless in PvE.
My solution is that everyone has 4 paths in the talent tree, instead of these ‘PvP optional’ selections, and there are more selections to craft your class. They will never do it of course, Blizz will continue to make this game less fun.