As explained on the official forums by Community Manager Josh Engen, Mercy’s will no longer get a free cooldown reset after using her ultimate.
According to a report by GamingBolt [VIDEO], Mercy’s Resurrect ability was too good, especially when paired with the ability Valkyrie. Previously, whenever Mercy went into Valkyrie mode, the cooldown on her Resurrect ability dropped from 30 seconds to 10 seconds, which let her quickly Resurrect multiple characters.
In the new PTR, Mercy’s Valkyrie ability no longer resets or lowers the cooldown of her Resurrect ability.
Several “Overwatch” players who like to use Mercy are disappointed for the new update. “Instead it now doubles Resurrection’s range”. That way, she doesn’t have to be in harm’s way when trying to bring back a teammate from the front lines. The buff might have been a buff too far, though, because the PTR is now testing a Mercy-specific change for this very exploit. Right now, she reigns as the most-picked Support character in the game ever since her recent rework. The Dragonblade ability of Genji now slashes faster along with his Ultimate ability. The RIP-Tire ability of Junkrat now moves slower. The Dragonblade still continue even when Genji is stunned.