Depends on which version of the game that you are playing. If you have access to Nightmare Mode, it is suggested that you get a good Mythical weapon that pierces multiple enemies such as the Bone Bow, Disc Thrower and Blunderbuss. If you're playing on console and don't have such luck, Blasticus is still fair although it does not pierce enemies. Once you have a weapon that you're satisfied with, upgrade only the attack if the clip size and reload speeds are good enough as they are. If you have a negative reload speed, upgrade your clip size enough that the long reload times will not usually be an issue.
Your Piercing Shot is a very good skill to use in conjunction with any sort of weapon you're utilizing, so try alternating between shooting and using the Piercing Shot every time it cools down. Use your invisibility to maximize your effectiveness in groups of enemies, but watch out for splash damage and incoming Dark Elf Warriors, as they are not affected by the Invisibility.
All in all, you can be an effective DPS Huntress if you tailor your stats into Hero Health and Hero Damage and find a weapon that supplements these skills while also being effective in its own right.