We're also very happy with Divi Tiara, went twice. Excellent operation, good boats, great crew and lots of different sites. Their packages are a very reasonable deal. We just stayed at the resort, so I can't comment on the rest of the island, but came to dive only anyway. Valet diving (drop the gear at beginning of the week and they take care of everything) but be sure to sign up for the trips you want quickly each day or you might end up diving the Tibbetts Wreck more than you want.
Another plus is the Cayman Air 737 from GC is only 15 minutes and no "bumps" to worry about. The props could be a little rough (if that bothers you.)
If the weather's good try to get to Amphitheatre (just what it looks like) on the South side or End of the Island, a shallow dive on the West point near end of the airport runway. It can be a rough ride to Little Cayman sometimes (1 hour plus), but worth the trip. But if Bloody Bay Wall is really your goal, stay at Little Cayman Beach Resort. Maybe $500+/week more pp than Brac but much better food and Blood Bay all week.