Without the sword skills, (32 hit combo!) there probably isn't a huge advantage to dual wielding. Even though Kirito's had a lot of practice, it's probably pretty still a difficult thing to pull off, and the biggest advantage it gets you is just the fact that people aren't used to fighting someone dual wielding. (And using it to cheat Eugene's sword.) So the "surprise" is really the only reason it's effective at all. Had Eugene been a shield user, he probably would've been able to give DW!Kirito a lot more trouble, just like Heathcliff.
Also man, Kirito has absolutely no problem lying his ass off at the drop of a hat.
