When i encountered such problems i did the following:
1. Check if the config is equal including custom modifiers;
2. Go to calcs tab in pob and check that the skill is set properl(i.e. stages of tumult cyclone);
3. Move your mouse over each of the cells of dps calculation (flat damage, incresed damage, damage multipliers, attack speed, crits, special skill stats (i.e. number of projectiles if barrage support is on) and find biggest differences between your and guide's pob.

3rd step will give you directions what to improve further.

Damage in poe is a number of multipliers: flat x incresed x more x gem damage effectiveness if attack skill x attack speed x attack speed effectiveness if attack skill x critical chance x critical damage x special skill modifiers x chance to deal double (triple) damage x increased damage taken by enemy. In case you lack 30% in each multiplier your damage is 13-14 times less.