I have a lvl 250 arge with over 600% melee damage that gathers significantly less chitin than me with a metal hatchet (about 3 times). I have a melee damage stat of 300%. I have messed with the harvest amount and dino harvest damage settings a bit and i cant seem to get it to work. Currently harvest amount is set to 5 and dino harvest damage set to 10. Im not even sure these are the right settings to mess with. I just want it to be more worth to harvest resources with a tame rather than my hatchet or pick....

Chitin, and other special gathers (such as hide, berries, prime meat, etc.) are weighted really funny with ARK, and in the case of specific tool weights, you'll find the default tool of hatchet is what's mapped to an animal's primary attack. Very few dinos have alternate attacks which work like other tools.