Atol's not wearing off at the same time?
 

Cast:
[Mon Mar 03 13:36:16 2014] You begin casting Atol's Spectral Shackles.
[Mon Mar 03 13:36:19 2014] A frost giant savage's feet are shackled to the ground.
[Mon Mar 03 13:36:19 2014] A frost giant's feet are shackled to the ground.
[Mon Mar 03 13:36:19 2014] A frost giant savage's feet are shackled to the ground.
[Mon Mar 03 13:36:19 2014] A frost giant's feet are shackled to the ground.

Wore off (two had died):
[Mon Mar 03 13:38:51 2014] Your Atol's Spectral Shackles spell has worn off.
[Mon Mar 03 13:38:54 2014] Your Atol's Spectral Shackles spell has worn off.

not sure if it's a delay in the tick but these should wear off at the same time?

Have noticed this with the lvl 29 snare, too. Usually just a tick or two difference, though once it wore off about a minute early on one mob.

All entity's within a zone have their own separate tic timers (6 second increments).

This is also not a velious bug, nor would I believe it is a bug (Working as intended).

Please continue to test issues, but please work with your fellow players about what is considered a bug, and what is specific to velious. I appreciate your beta testing but this is the second thread I've moved.

Yep, This also explains why all spells cast on mobs will vary slightly in duration. You'll see this behavior on every AE CC. As mentioned, not Velious specific.