They have a new rare dropped power source this expansion that is a lot better than any of the old ones. However, you'll drain it long before you ever found another one.
FYI if anyone is curious: i went from voa T3 raid armor to rof T1 raid armor, one slot at a time, and each new slot of T1 armor i added increased my HEM and heroics, despite the loss of stats to the emblem on my BP (which was the last item to go) if you're in voa T4, it'll equate to a per-item downgrade (after emblem) until you have a full set, at which point it would be a very minor overall upgrade.