I personally don't miss dual-wielding. However, more weapon variety in campaign (especially in the later missions) would've been nice. Seems like it boiled down to all Lightrifle all the time. You're pretty much forced to plink away at Knights from long/medium range in order to survive, and the only weapon around with ammo available ends up being Lightrifles due to enemies dropping them. And because the Lightrifle is basicallya DMR wannabe instead of a unique, alien-feeling weapon, it just leaves me kind of cold.
Don't want to sound like I'm totally down on the campaign, because there was plenty I liked about it too. But I feel like there was so much unfulfilled potential in the Prometheans (combat behavior, "character"/lack thereof, and their weaponry).