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.
Crit and Surge "On Use" relics are a waste because of how easy it is to hit 30% Crit and 75% surge, you're pretty much better off to just use the BM/ WH Power relic with the On Use Power relic, getting all your Crit and Surge from Gear.
And while both specs have Talents that Auto-crit certain abilities, but there are only 3 abilities that auto-crit (Cauterize and Overload Saber burns with Zen, Blade Storm with Combat Trance) and they aren't "Auto-Crittable" often enough to make up for the impossible amount of power you would otherwise have to stack to counter the loss of dps from not having 30% crit chance unbufffed.