I've got to say, I've never found the Doppleganger to be that impactful. Cheating Initiative is nice, but I generally have my high cards earmarked for things before the initiative flip, and cheating the Initiative flip means one of those actions needs to rely on luck.
It's nice if you're in a situation were, for example, your master is about to get killed and getting Initiative can save it, but I haven't found cheating the Initiative flip to be as useful as some make it out to be.