If you only care about damage, get a bastard sword ego. There are dark blue bastard swords around, although rare.
180 max + 150 max(elsinore) = effectively 330 max damage, a 100 difference from a maxed 2h. With this you have more flexibility in your usage as well, although you'll probably just dual wield 24/7 anyway, knowing your playstyle.
More realistically, 180 max + 100 max(broad/battle) will yield you 280 max, effectively, a difference of 50 from a maxed 2h.
The downside is, yes, you do have to maintain another weapon. The upside is you have a higher damage rate, and badass final hit capability. And you at least have the option of a shield, for charging capability.
Very few downsides, imo.