Confused about dual wielding and aggro (warrior)

[Ransurian]

Low-level warrior here (14). I've been trying to gather reliable information on dual wielding and aggro, but the only consistent bit of advice I've been seeing is to use my "fastest weapon in my main hand" and my "best ratio weapon in my off hand," supposedly because of some sort of flat damage bonus associated with dual wielding when using a fast main hand weapon.

However, I'm currently using a Green Jade Broadsword and a Lammy that someone was fortunate enough to give to me. GJB has both a worse ratio (11/25) and is slower than Lammy (9/18), so what weapon should go where? Should I try to find a faster weapon than GJB? Am I gimping myself by not using a faster main hand weapon? Will my damage and aggro somehow significantly increase if I use a faster main hand weapon (even if that weapon doesn't necessarily have more DPS than GJB)?

Thanks for any helpful responses. I'm not entirely sure what this "damage bonus" people have mentioned is, and how it comes into play.