Bear in mind that it's not hard to give even a bare bones warrior priest a 5+ Ward through his prayer. But then, no one here but me seems to ever get their prayers off so it might not be the solution to you.
Some thoughts on this thread (mind you I played countless of battles in 6th edition and before and only two with Empire in 8th edition, and two with my Lizardmen)...
1. I don't find it hard to get a prayer off. Just tool up 3-4 Wizards and choose the right order and targets. If the opponent knows a spell is going to hurt him bad (say his chaff and lone models), then they will forget your prayers quickly. Even one dice has 2/3 chance to get a prayer through if the opponent used his last dispel dice.
2. I find that most large units rarely see more than 1-2 important combat engagements in a game. So I don't see any reason trying to avoid combat with the Warrior Priests. I would rather tool them out with a good save. Having a champion to accept challenges is good to keep the WP alive for the remainder of a combat.
