Yup, silasw has the right idea. In a format packed to the gill with guilds, what you'll actually end up with is primarily three-colour decks, not two-colour decks. By drafting three colours, you have access to three guilds' worth of goodies, which is a lot more appealing than only being able to play one tenth of the many gold cards on offer.
In general, I find that heavy multicolour formats tend to revolve around three-colour decks, whether we're talking about retail limited or high-powered cube.
In general, I find that heavy multicolour formats tend to revolve around three-colour decks, whether we're talking about retail limited or high-powered cube.