I'm not sure if this is old, or is even a bug.. I found no forum posts relating too it so I thought I'd post it anyhow.
So i found myself farming the Baron Rivendare mount from strat, after stripping myself nekkid and letting all the skeles kill me after killing Baron I ran back to the instance to revive, respawned, stuck all my gear back on and hit Rune Tap.
Then I ported out the instance and the Rune Tap cooldown was gone, so I used it again, then ported back into the instance and once again it had gone.
So I went to try it out on another instance.. ported to Dalaran and realised I didnt have the VH key on this toon, me being lazy thought fack it, cba ill go back to farming mount, then had a thought "what if the rune tap cd disappears on your character actually warping somewhere" (ie instance portalling, moving zones via portal).. so went to the dala portals, hit the rune tap, portalled and hey it was off cd again.
So I'm not sure if this was intended, but a cooldown is a cooldown right.. what use is this you say.. well so far ive found it ****** useful for health regen from reviving after farming the Baron Rivendare mount to get to full health, saves gold on food anyhow.
As I say i dunno if its intended or its old.. but yeah I'd thought id post it anyhow since I found zero references of it on here.