This is a legendary item with damage boosts. Legendary dagger or bow can have proportional damage boosts as well, so I'd say the percentage difference between the two will stay if you find equally good items. I've found 1h weapons with more damage than the item on the screenshot, so its a matter of how lucky you get
. I've intentionally used common gear to get a fair baseline.
Piercing resistance indeed seems to be more common than other physical resistances, but its at least nowhere near as common in the endgame as it is in act 1. I have loremaster to attest to that