Blizzard Representative Eyonix has revealed two new features of the Burning Crusade that will satisfy many players:
- Healing over time (HoTs) spells such as Rejuvenation and Renew will stack for every player casting them. For instance, if there are three priests in your group, a target could potentially receive three renews as one time.
- Warlock and Hunter pets damage will scale up making pets stronger as the player gains more statistics through itemization.
Source: Wow Forums
