Phantom grip question

[crowgo]

Hi, I was watching a FM playing the other day on twitch and I realized that he would often phantom grip a player, RMB or just let the time run out, and once the player is on the ground getting up he instantly casts a Frost palm + Impact.

 

I tried to do the same, on players and on mobs and I found out that by the time I can cast them the mobs/players already got up, I tried this over and over and the global cooldown(or something else) just won't allow me to do it. Am I doing something wrong?

I ping 50ms to the Dallas servers if that helps. 

[crowgo]

bump

[InoriYuzurihaDesu]

I hardly pvp, so im not sure, and as for pve, im a glass cannon, there is really no point for me to grab anything besides dpsing.