Good bow upgrades?
Sigil of Force is a solid choice, just a flat 5% increase in damage dealt. Since you are running a zerker set up, you could use Sigil of Air to increase your burst potential (it deals an extra 1-2k dmg on crit every so often). Those two would probably be safe to run in almost every situation.
Alternatively, you could run Sigil of Strength to give yourself some pretty solid might stacks, or Sigil of Fire which deals less damage than Sigil of Air, but does it in a small AoE. These 4 are generally the accepted ‘high direct damage’ setups. You could then roll Sigil of Energy and Sigil of Bloodlust on your second weapon set. This would give you half your endurance whenever you swap to your second set, and killing foes with your second set will increase your damage with both sets.
For more defensive situations, you could run Sigil of Generosity which would transfer a condition from you to your target when you critical, or Sigil of Ice, which applies chill on-hit which will let you kite a bit better.