Its a win condition in my deck and it works. Emperor made the card somehow viable. I know its not a candyland to prepare such a complex combo, but my deck has, similar to freeze mage, a crap ton of card draw and sustainability, which makes it very strong against the archetypes you have in mind especialy
Hunter for example is a joke to play against most of the time, yesterday I was constantly bad mannering 1 of them by spamming threat and highlighting my face with mouse cursor. The guy had bow on 1 charge and a secret, i had some minion on board all the time and I didnt attack for f@#! knows how long. He only used that last charge from the bow once he got another one in his bottom 10 cards. I was allways above 20 health, I went to fatigue, ive drawn cards in fatigue for 0 mana (thx to 5 triggers from my emperor) just to BM him, Ive alexed him from 9 to 15 health, so you might say that velen isnt even a win condition against this one in some cases
Its not an ultimate deck as it has its weaknesses and a really bad ones, like warrior or druid, or even freeze mage, but hell is it not fun to play and accept all these friend invites from people to ask you WTF WAS THAT. Overall Velen isnt great, it needs something else for it to bring some value, and most of the time you gotta unleash that the turn its played coz obviously its the primal target to remove, but the thing with priest is that it lacks burst and noone really expects you to hit for 20+ damage in a single turn with empty board (which might be kinda obvious in my deck but still) and so it can work if used correctly.
https://dl.dropboxusercontent.com/u/43525724/Hearthstone%20Screenshot%2006-13-15%2007.46.21.pngThats my decklist but please dont share.