Hitting a 3000-health target with 50% resist would deal at least:
175 minimum + 300 max hp bonus damage + (40 + 6.25 scaling bonus) = 521 damage for the attack
50% resist - (30% + 6.25% resist pierce ) = 31.875% resist
= 354.93125 damage
Assuming you have strong spirit investment, and have 150 total spirit by this point:
175 minimum + 300 max hp bonus damage + (40 + 37.5 scaling bonus) = 552 damage for the attack
50% resist - (30% + 37.5% resist pierce) = 16.25% resist
= 462.3 damage
It's probably op but needing to charge every 12 seconds like Express Shot would balance it out I think