Hearthpwn

I'll use myself as an example in the current meta as I completed my legend grind last night playing 100% of my games from diamond rank 5 to legend with Quest Malygos Warlock (though the deck I used is irrelevant here). 

I was using deck tracker while doing this, so I have some data on the grind. The piece of data that's relevant to your question is that 14% of my 81 games played (a few were actually played at legend, but not many), were played against Priests, and all of them were post-nerf patch. 

So, if you were to have a similar sampling of classes as I did, that's 14% of your games that you would automatically have to count as losses. That may not sound like a lot, but if you only have a chance of winning in 86% of your matches, then you would basically have to maintain a 58% winrate against everyone else in order to have an overall 50% winrate. Bear in mind, that's a 58% winrate just to BREAK EVEN. If you look at Hearthstone replay, Highlander Mage currently has an overall winrate of only 52.79%. That's only data from the lower ranks of the meta and thus better players might have higher winrates than that, but still. The difference would not be extreme. 

Long story short, conceding your matches against all priests would make your climb to legend statistically almost impossible. Even if you feel like you're saving time by doing it, you're still shooting yourself in the foot.