Stack power? Stack willpower? In my opinion neither. Choose your crit and alacrity cap and stack power and surge after that. Simply balance your gear in a way which suits you best.
My stat preferences are 40 % crit and 6 % alacrity.
My surge goes 78.75 and bonus heal is on 818.
Those 2 previous builds were very good but I think that you will be more efficient with 4.5 % crit and 3.5 % surge than with 3.2 % alacrity and 15 bonus heal
With this build you are like a healing catapult (offten and powerful crits)
This is my current gear build (click on wish list)