This bug fix can have a significant impact for both Zarya and Symmetra beam damage and to a lesser extent Winston and Moira. It will make damage feel more consistent but does not increase their maximum damage.
The issue was that if you were tracking a target with a beam and then lost it (within about a 0.15 sec window) it could end up dealing a partial damage value instead of the full amount.
The odd part of this fix is that the damage increase scales inversely with tracking accuracy. The more accurate a player’s tracking is, the less noticeable the change will be, with professional players likely being the least affected.
We’ll be keeping a close on eye on Zarya and Symmetra in particular this patch.