today in ToC25, a wipe was called. and as all mages/rogues/hunters do, we try to survive and avoid the corpse run/repair bill.
i used invis, as you do, and just as the 3 seconds were up, anub charged to me, he slapped me with a melee, yet it did no damage. but combat log still recorded a 55k hit on me.
this may be useful somewhere, but where i am not sure.
hope this is useful to someone.
so in short. there is a period within the transition of invisibility where you take 0 damage.
edit: after testing i have found that is it the transition between the 3sec countdown and the new buff. its damn near impossable to time with untalented invis (my screen was complete luck) but talented it is slightly easier to recreate.
but keep in mind the server registered me getting his for over 55k, but it didnt take the health away, wtf >.<"