I did quick search did not see this. It may be intended but I thought it was worth mentioning since at least to me it did not seem to be working as it should.
I noticed this yesterday, perhaps it was in the game before 5.2 perhaps it was not.
When you death griped someone who was mounted while being mounted pre-5.2 it would pull them to your position when you cast the spell. Currently though it seems to work differently. Your target will get pulled all the way to the ground even if you where 30 foot in the air when you death griped as if they had inertia.
I am now sure why this is, I am hoping they are following you until they reach your location. If this is the case there is alot of fun that could be had especially if you could move faster than they could catch up to you.
As I said though I am just going on my observations yesterday, perhaps you can find out more.
If this has already been posted feel free to remove it np, if it is new and you agro it is not working as intended feel free to move to elite. This had alot of potential.