I'm not sure when that changed, because a while ago, the resizing was very smooth.
But with the tip, if you resize your plugin (using the ResizableCornerComponent) in logic, the GUI is flickering a lot, like jumping on the y axis.
that can be reproduced using the JuceAudioPlugin
Are you sure this is a JUCE change and not a OSX10.11 change? As mentioned on other threads, Apple have done something weird to the way events are dispatched, which is causing a lot of odd edge-cases in the way hosted plugins behave.
yep, I'm on 10.8. (and with the same logic version as before)