I think your recommended Critical Rating of 350 is too high. I have calculated exact stat weights for every ability, and in BH/Campaign rating gear, the optimum value of Critical Rating appears to be more like 150-175 (this is with about 1950 Strength and 800 Power, unbuffed). Both Combat and Watchman have talents that cause key abilities to proc autocrits; when significant amounts of the spec's damage comes from auto-crit procs, that tends to favor Power over Critical Rating. If I were to follow your suggestion and increase my Critical Rating by 175-200 points by trading Power, my average damage would go down by almost 1%.
I'd have to agree. I've been debating with other Sentinels in my guild about this, but the thing we often forget to take into account is when you use your relics it adds critical rating, surge rating or power rating (assuming you use the active ones); and if you already have 350 CR then you activate your relic, most of the "benefit" of the relic is lost to diminishing returns. In addition, LagunaD makes a solid point about auto crits. Both specs have auto crits and CR points are essentially wasted at that point, better to spend them in SR or PR.