Logged a run of Stormstout Brewery today. Looking at Blackout Kick we can clearly see that it is not stacking linearly at least.
[13:42:48.368] Daecaran Blackout Kick Hoptallus *31950*
[13:42:48.368] Hoptallus afflicted by Blackout Kick from Daecaran
[13:42:50.368] Daecaran Blackout Kick Hoptallus 3195
[13:42:51.318] Daecaran casts Blackout Kick on Hoptallus
[13:42:51.578] Daecaran Blackout Kick Hoptallus 17787
[13:42:51.578] Hoptallus's Blackout Kick is refreshed by Daecaran
[13:42:52.358] Daecaran Blackout Kick Hoptallus 4266
[13:48:33.098] Daecaran Blackout Kick Yan-Zhu the Uncasked 14358
[13:48:33.098] Yan-Zhu the Uncasked afflicted by Blackout Kick from Daecaran
[13:48:35.088] Daecaran Blackout Kick Yan-Zhu the Uncasked 2871
[13:48:37.028] Daecaran casts Blackout Kick on Yan-Zhu the Uncasked
[13:48:37.088] Daecaran Blackout Kick Yan-Zhu the Uncasked *32680*
[13:48:37.088] Yan-Zhu the Uncasked's Blackout Kick is refreshed by Daecaran
[13:48:37.088] Daecaran Blackout Kick Yan-Zhu the Uncasked *6338*
[13:48:39.088] Daecaran Blackout Kick Yan-Zhu the Uncasked *6338*
[13:48:41.068] Daecaran Blackout Kick Yan-Zhu the Uncasked 3169
[13:48:43.089] Daecaran Blackout Kick Yan-Zhu the Uncasked 3169
World of Logs - Real Time Raid Analysis