Well Im not the type of person who does the math, and tests everything out, that being said, I just cant see how 47 power, would be more usefull then 84 Will, with an additional 27 crit.
From my understanding Power is very similar to Will power, but from what I can see, willpower also helps critical, and as its my main stat, I believe it makes it a little better than power.
Now I have read that at somepoint, Willpower starts giving diminished returns, but even then, with almost double the Willpower I think it would still be more helpful than 47 power.
I assume you know more about it though, so I would be interested in knowing why its not BiS, or why I would be better with a WH relic then the Matrix Cube. Your help is much appreciated