I am not surprised that D76 worked well. It's an old, established developer, and PhotoEngineer has stated, that every single B&W film about to be released is tested&verified against D-76. What did surprise me were your alleged inadequate results with HC-110. This is a standard developer and marketed as substitute for D-76, and it offers a wide variety of dilutions and development times. If HC-110 stand is your thing, but too flat, crank up concentration until contrast is where you want it.