This is buried in my Thrower build thread in my signature so I'm posting here:
"Heroic Feats" are Rapid Shot and Quickdraw, which each give around a real world increase of 15%, combined it's about 25%. I have not done these tests to see what throwing rates would be at Epic without these Heroic feats, but I'd like to try to do that next.
Eventually I'll update the picture, but Ranged Alacrity, 10% from Cannith Crafting DOES apply exactly as expected. 5.57%, or .933 Sec/Throw vs Baseline (Nothing, above).