I have the same issue with my MBP Retina 975 which has not been able to stream video/sound smoothly to my only Apple TV (an ATV2) since upgrading to Yosemite.
I have seen numerous posts from 2014, and now yours, which seems to be recounting the same story, however, there does not seem to be an answer which relates to ATV2 specifically.
There are some reports of changing the PRAM and turning off Bluetooth solving the problem (with mention of ATV3).
I have updated software in all devices, tried turning off Bluetooth, and this had no effect, I am however reluctant to change my PRAM unless it is an assured solution. I have no idea what side effects there might be.
The Communities sites have fallen silent for a year (apart from your post) and it seems odd to me that Apple would not try to solve this in an update, perhaps they have for ATV3? .... but it is not going to happen for ATV2. I would be interested to know which release your many ATV's are.
If my Apple TV2 is now defunct / out of date I will simply bite the bullet and buy a replacement, but I don't want to do so only to find that there is a cure later.
Any advice on the status of this issue and hopefully an answer to my particular problem would be most welcome. Thanks Martin