Yeah, not a fan of sanctified slayer. Studied target is very micro-heavy, and before you go "but you study things automatically when you hit them", yeah hitting in order to get an AB bonus is backwards, especially when you're a mid BAB class with less AB and less extra attacks to take advantage of study with. For a large portion of the game you're gonna hit once, maybe hit the next attack, then the rest of your party kills the target. Repeat for every further target. In this scenario only half of your attacks are getting the studied target bonus. Their sneak attack progression is also super awful, anything with Sense Vitals basically equals it.
Not sure how you can say SS is good early game. You don't even get your first sneak attack dice until level 4 (at which point, wow, 3.5 damage on a mid BAB class with no AB boost), and studied target is as I mentioned very weak until you're getting lots of follow up attacks or are prepared to constantly swift study.
Clerics on the other hand are full spell casters, still mid BAB, 2 domains (which is huge, your first mythic abilities are spaced super far out so we're talking several levels ahead in development). One decent domain, lets say Nobility because its an easy comparison, is benefitting your party way more than studied target is.