For the record, this is pretty much opinion. Crit and speed, as in any game, appear to be equally ranked theory-wise. Stack the one you feel fits your style.
From
http://valk.dancing-mad.com/?page_id...alingmechanics the following are the returns:
An increase of 30 magic damage returned approximately 3 points of healing for a .3 return (some also report 1.5% increase). 1 point of Mind will produce approximately .2229 HP of Cure 1 and thus Physick. Determination will increase healing approximately .06 for 1 point.
In using the calculator, you should be able to expect a point of magic damage to give roughly .83% healing, mind giving .70%, determination giving .15%, and crit giving .04% increase.
So by this math, prioritize magic damage, mind, determination above any other output increase stat. Then because we like having MP from which to cast and recover, you'll want to immediately prioritize ability to put through.
Weapon damage > mind > determination > piety .
Now, that leaves us with the discussion between spell speed and crit. We have seen that crit only gives about .04% per point increased which is pretty small. We know that spell speed gives about .01 GCD for roughly 10 points. However, you cannot directly relate spell speed to potency without testing various combinations of damage, mind, and determination. SS, like all other stats, appear to be linear in nature 100 points will give you .1 GCD off., 1000 will give you 1 point theoretically (no signs of curvilinear relationship, so assume linearity). It appears approx. 20 spell speed gives you .01 off Physick.
So, it really comes down to personal flavor at this point. Is the per point .001 GCD decrease and .0005 cast time decrease better than the .07 crit chance for you and what you need? 'cause there's no data on how spell speed increases healing percent-wise.
Which leaves us, in my opinion and after viewing the math, with the following priority based on desire to put out numbers followed by desire to be able to put out numbers:
Weapon damage > Mind > Determination > Piety > Crit and/or Spell Speed