I was under the impression that on use relics of the same type share a cool down; is that not true?
The BM/ WH relics are Static (+103 power or +113 power). You don't have to click them to activate.
The average damage each ability does based on your stats, including crits, DR, etc, is just a big formula, and the formula says 300+ Critical Rating is not optimal. Only about a 1% worse than optimal, but not optimal.
1. This thread is titled Basics. Not really worried about "Optimal" especially when "Optimal" is such a minuscule difference.
2. If you're wiping because you're 10-15 dps (1% of median Sentinel DPS range) short, you've got other things you need to look at such as group composition, healer gear and ability, tank gear and ability, and what's going on with the other three to eight DPS in your group.