I recorded videos of me shooting rockets at Crota on hard mode. I then tried to calculate the damage done by stepping through video frame-by-frame. For the Gjallarhorn I counted 5789 damage. The HoC is harder to count, I estimate the damage output to be in the 2500-3500 area. Crotas shield seems to have 15k hit points. I can't find any confirmation on this though. Crota himself is widely reported to have 250k hit points. Here's a video showing my tests, zoomed and slo-mo. http://filebin.net/sagrnbzmg6/Gjallarhorn_vs_HoC.mp4