I always thought Precision bless would be pretty awesome, but it does seem that it could be highly abusable. One the one hand you have nations with strong evocation mages that are hard to kill, like Agartha, whose weakness is low Precision. On the other hand, you have Air nations, whose mages already have excellent Precision, who can take an Air bless, and then use Storm with impunity to wreck your Precision, while theirs stays nice and high.
Not to mention the wacky synergy between E+A bless, for sacred mages. Tell you one thing, if you don't fear R'lyeh yet, you would with that kind of bless.
Ultimately I think blesses aren't meant to change the mage balance very heavily, but I don't know for sure.
