Destiny is a tough cookie for rapid fire because every gun is tuned in game differently. (This means a different rapid fire for EVERY weapon) but not only are the guns tuned by the game devs, they are often updated which changes things again then to top it off the games has a speed cap on each gun.
I will look into the Thorn this weekend and see what I can come up with. To speed the fire rate, it will have to implement a "humanized rapid fire" to do this, instead of the one trigger pull then repeat, it needs a long trigger pull, pause, then short pull, pause and a longer pull then repeat. but timing and lag is the key. Then once I get it done, the next update could wipe all the hard work out.