I ' m not agreeing with OP ' s suggestionin fact I ' d rather have Mercy just have the highest healing output with the least utility as it seems to be her characteristic , I ' m only saying that Mercy isn ' t the only hero that can shut down enemy ultimates , reactively or otherwise . Mercy doesn ' t shut down an enemy ' s engage any more than other heroes already can . Mercy doesn ' t care what you use as long as she isn ' t caught in it , and she can wait until the threat is over without having to rely on reaction timing if she already got to a safe spot before the engageThat ' s the problem , staying alive when the enemy knows you ' ll be waiting somewhere . A smart opponent will send someone after you , so you ' ll have to deal with a flanker that ' s going to be chasing your ass down . And if this happens , you ' re dead , because you can ' t guardian angel because you ' re hiding . Furthermore , the enemy can simply not blow all their ultimates before you blow yours . They may blow one or two , but wait for the res before using the rest .