I followed all of the tips. Prime sirloin, taken out an hour before cooking. Salted thoroughly 30 minutes prior. Patted dry with paper towels. Thrown on a high (650) degree grill for two minutes per side, finished on low for 3 minutes per side (internal temp was still about 400). Rested 10 minutes.
Results: Good sear, beautiful medium-rate insides. Plenty of juice. Enough salt.
Problem: the exterior was almost like bark. It wasn't scorched or burnt, but just really really dry.
What was the misstep?