What I see as a main problem between priest and priestess is their difference in channeling. 9 is so much worse, that the other abilities or his playstyle should even that out.
I'm not a 9-mana hardliner but I do have the feeling that giving the Priest 10 channelling is too simplistic as a solution and may in the end not make any meaningful difference as his abilities are still subpar.
imo AW's reasoning that the more aggressive mages channel 9 mana and the less aggressive channel 10 makes sense, and the Priest is supposed to be in the aggressive category.
That's why I think we don't need to change his channelling but to give a serious boost to his abilities.
Looking at his abilities it's not too hard to see where they are flawed ( requiring damage - thereby making a Defense a "handicap" - and not triggering when the HA is attacked himself ) or where it can be improved ( make the Burn free )
However, that would still not be enough, I think. He would still need more "bang".
So, what if the Holy Avenger came into play
active ?
That would mean no tempo loss for the Priest, as he can summon and attack with the HA the same round.
It would allow him to walk straight into battle and summon the best possible HA there right on the spot and still have an attack that round.
If you think about it, it would be the Priest's alternate to Reanimate.
If the Necromancer loses his Servant all he has to do is pay up and the creature is ready to activate again next round. No round wasted on casting it again.
If the HA were active right away it wouldn't be such a loss of tempo each time he has to summon a new one and it actually would make sense to summon more low level Avengers.
Under the current rules you want to summon as few as possible HA's since you'll have to waste a full cast on it every time and both are not attacking that round.
Under my suggestion the full casts would hurt a lot less and it would actually let you gain more life out of the Ha ability. Summon 4 HA's and you've gained 20 life from it ...
At the same time the Priest should be a mage who's not afraid to be in the eye of a storm as he has Holy protection.
That's why I suggested to give his basic attack also the Damage Barrier trait. Whoever melee attacks him should feel his wrath.
EDITED
Rather than a damage barrier, I think giving him the Vigilant trait would be an even better way to illustrate and effectuate this.
A Guard marker at the end of each activation to allow him a possible extra melee attack could be a great deterrent.
This may all take a lot of words to explain here but on the ability card it really wouldn't take that much space and words to implement at all ( see reply nr 17 above ).