Just before SSK was introduced, there was a bug with Build Up Procs firing while exemplared. They would indicate they fired in the chat, but the actual buff was not applied when you watched the Combat Attributes.
I hope that bug isn't back. I'll keep an eye out for it.
Edit to add: I just did a test while exemplared and both the Gaussian's and Decimation BU procs were firing and buffing as usual. I was watching the chat and combat attributes so I wasn't watching to see if the buff icon winked out early though.
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"Chew Electric Death, Snarling Cur!"
My 50 blaster has both Gaussian's chance for build up and Decimation's chance for build up slotted. In PvP zones, they don't seem to have any effect, I see the icon flash once in my status bar, then vanish. A similar effect appears when exemplared. Does anyone know why they are behaving in this manner?