"worst ultimate in the game"

I love the hero comparison threads that exclude everything except from what is convenient.

It is convenient to compare Mercy’s ulti with other supports, if you exclude how much time she needs to build it.
It’s also convenient to forget that Mercy still has the best support kit given a simple risk/reward analysis.
Finally, it’s also convenient to claim that boost isn’t powerful because there are no metrics.
Most importantly, I wonder why pros still use Mercy even in compositions without Pharah. Let me guess… A pro Mercy can dodge pro Tracers with more ease… No, no it doesn’t feel right. Her ultimate becomes monsterous in the right hands, like dragonblade… No, no… Please tell me why would a pro team choose a “crappy” hero like Mercy over a Moira, Zenyatta, Lucio or even Ana?