Any team worth their salt will just wait for the 15 seconds to expire (of course you can try to revive during that time, but I doubt they'll allow you to do that). Btw, spirit of redemption used to have a 10 second duration. It was increased to 15 seconds, because a lot of players complained about lag causing them to not be able to cast during the first couple of seconds. What I'm trying to say is, you're probably better of with a tactic that doesn't depend on your healer being dead