I see some topics that allude to an old proximity Gruul's addon that was superceded by the proximity in the master BigWigs, but that doesn't address the other boss timers associated with High King/Gruul.
Can someone point out where these are (assuming they exist)?
The Gruul fight is part of the standard Bigwigs release (Gruul.lua in the Outland folder). There used to be a separate addon called GruulAssist but I'm not sure what it was good for and it was giving me errors so I deleted it... I'm still getting warnings and a proximity window (make sure you enable that in the BigWigs menu).