In terms of gearing...

The first page mentions:

"As with all Inquisitors, Willpower is your primary stat, and you use both physical and Force abilities, so you would rather take the Power statistic rather than Force Power. You do not need Alacrity as none of your abilities of note have cast-times. Critical Strike Rating is your single most important statistic, as your critical hits with Maul, Discharge and Shock do significantly more than the base +50%. While Surge Rating is also nice, you flat-out crave critical strike more than anything else until diminishing returns kicks in hard, because you have no method of ensuring critical strikes to keep Exploitive Strikes up aside from Force Potency.

Surge Rating is still valuable as well, because the built-in diminishing returns on Surge do not account for your flat bonuses to critical from your specialized skills. You can easily sport another +20% critical strike damage from gear."

Is there any math on how these skills equal each other?

For example, should I give up 10 willpower to obtain 20 critical? or should I give up only 5 WP to obtain 20 critical?

At which point can we give up WP for Critical Strike Rating is reasonable, and vice versa?