The problem with Crit though is, Crit = random overheals. Likewise unless you are shielding as an astro... random overheals are NOT useful. While clearing raid content your goal is to cover survival and recover damage as quickly as possible while minimizing overheal. Crit is useful when shielding or when hit point pools are so large that a random crit = one less heal. FFXIV isn't really designed like this... its EXTREMELY spam happy. Consequently I strongly disagree with padding crit unless you are shielding.

Likewise current raiding content, the most important thing is that you reach your position and your next heal hits in time. That is spell speed hands down. Once you learn fights and tighten up to where you know the heartbeat of a fight and its exact rotation, then you can let up off spell speed. But by then you're learning a new fight where you benefit greatly from said spell speed.

If Determination carried more weight I might put it before spell speed but it does not. So I strongly encourage (whitemage slot) Astrologers to go Spellspeed > Det > Piety/Crit.