Level up lancer to 34 for Blood for Blood (extra 20% dmg but you take more damage, not to use after p1)

You are forgetting Barrage.
Also make sure you cast your buff BEFORE your dot (this has the most impact on DPS). Don't refresh time until they are expired.
Always use heavy shot over Blood Letter. Only use Blood Letter as a filler between GCD.
Don't use mana song - It should not be needed except in late p3. Foe Requiem +Battle voice on p2 (heart phase)
Make sure you are being cured after being release from cage (you get a damage debuff)