I ran into this issue last night, tried to open a ticket, but after an hour the raid ended and I logged out before getting a response.
I found that my Soulstone wasn't lasting very long on whoever I cast it on. The duration was reduced to 15min with 3.3, and maybe something went wrong.
1st attempt - cast on a priest in ToC, it expired in 2 seconds.
2nd attempt (15min later) - cast on the same priest in ICC, it expired in 2 minutes.
3rd + 4th attempts - cast on a druid in ICC, both times expired in about 2 minutes.
All four examples were completely out of combat, with the last 3 making sure they didn't click it off.
Has anyone else noticed their soulstone falling off the players they cast it upon quicker than intended? (I never did try it on myself)