What is the dmg boost attribute?

There's 2 types of base damage increases. The one u speak of that is in % form listed with your other stats and can range from 0 to 80% (as far as I've seen screen shots of from u.s. tcp servers) do not cage your visible damage total so I assume they go into affect upon player using skill/casting. There is one that does make your overall dmg number go up that's visible to you in toon gear/backpack page and also found in your stats. It's obtainable through belt equipment combination bonuses to that specific gears assigned damage value, with it found upon inspecting each gearside stats and scrolling to very bottom. This same type of buff can be rolled/won when applying grand attributes to gear. IE: Gears damage is increased by 15%. To make it even more confusing you can also roll/win overall dmg % increase usually in the 3 to 5% ranges. These are identical to first discussed and do not visibly make your overall dmg go up in value.