i am just wondering exactly what the stat which increases skill damage works (aka increases sweeping wind damage by 15%) does the percentage just simply get added on to the base 105% dmg sweeping wind does?
It's additive with the same multiplier, multiplicative with others. If a skill does 600% damage, you will have a skill that does 600x1.15=690% skilldamage. If you have 30% skilldamage, you get 780%. What you say is partially true. Stacking just one stat isn't as good as spreading it. That's what Quin is saying. But skilldamage is a separate multiplier in the total calculation.