Vampiric Embrace healing buffed for 25M in 5.3

Looks like the 25M healing buff has also reached shadow priests.  Their Vampiric Embrace will now heal up to 15 raid members, up from 6 members on 25M only in 5.3.

This could up a shadow priests healing significantly for 25M, and will definitely help healers out, especially when under-healing content.

This change was a late addition to the 25M healing CD buffs from a few weeks ago that saw Divine Hymn, Tranquility and Revival all get buffed when used in 25M instances.