Acquisition Rates
Roughly 6 gems per cluster, range of 3 to 9 with a bias towards 5 and 6. Heroic mode drops the same amount as normal mode.
clusters per boss bosses to complete bosses to complete
Cluster Clutch Sharpening Your Fangs
10 man 1 52 60
25 man ~1.9* 28 31.6
* ~10% chance for 1, ~89% chance for 2, ~1% for 3.
Gems within a cluster follow a rudimentary bellcurve when placed in a bar graph. You have a high probability of acquiring 5 or 6 gems, with a minor chance of anything outside of that. There's an average of roughly 5.9 gems per cluster.