I'm still going back and forth on dipping into Bard. If I decide not to, I'll only be making a few minor adjustments.
Drust is one of many sons of a peasant farmer run off to war to escape the tedium of peasant life and earn some glory. His weapon is simply a modified threshing flail, and most of his other gear is scavenged from the battlefield. Being rather fleet of foot, Drust was also frequently used as a runner.
How he meets up with the rest of the party probably depends on what kind of fighting has been going on in the region. I'd be down for a dark past, with Drust being one of the routed survivors of a failed rebellion or coup. Whatever works for the setting, really.