We're having an issue with Pro Tools 12 and our AAX plug-ins. When the plug-in GUIs are open PT12's own GUI becomes really sluggish (for example the timecode update begins to stutter). This seems to happen when the plug-in GUI is requiring a refresh; if the plug-in needs to be continually refreshed (because they have meters, for example) then the Pro Tools GUI is always sluggish, until the plug-in is hidden.
Pro Tools 10 is fine, so this seems to be a 64-bit, Yosemite, PT12 issue...
I have tried several different approaches in the code but cannot find a solution.
Even with the protection code compiled out the problem remains. It seems to only affect Yosemite. I searched on the Avid DUC and saw a few similar reports, but most of them were resolved with Pro Tools 12.2 and Yosemite 10.10.4.
So switching to OpenGL to render some of the elements seems to have solved it for now. But it also introduced some graphical artefacts. Sometimes the outline of a component's bounding box is visible when it's being moved.
I had the same problem today, in my case I had 6 paths each having an "addPieSegment" refreshed with a 40Hz timer. Shouldn't be a problem for the engine, but it's as you describe it, all ProTools GUIs stutter even over seconds... Happens on OSX 10.9 as well.
I will check if it happens with all paths or only PieSegment.