Speaking in a developer update, Jeff Kaplan announced the following changes to Mercy’s kit:

Resurrect is No Longer an Ultimate – That’s right, we’re going to be hearing “Heroes never die!” quite a bit more, as this has now been changed to Mercy’s secondary ability. It’s on a hefty 30 second cooldown and has had its radius decreased to five meters. This seems crazy powerful, but will stop some of the gimmick plays that were being seen in competitive surrounding her old ult.

New Valkyrie Ultimate – Mercy is going to be able to fly, not like Pharah jump pack flying; for twenty seconds, Mercy is going to be a fully directional avian menace. In addition to the sweet ability of flight, both of her beams (damage boost and healing) will now chain between allied heroes, and her gun will gain increased damage. In addition, as soon as her ult is used, resurrect’s cooldown will refresh.

Overall, this is a huge kit rework and initially seems very overpowered. Luckily Blizzard is going to be testing it on the PTR before it goes live, and some of these abilities may see tweaks.