viaduct is a pretty big exception in that you pretty much always want two scouts so usually either the roamer goes sniper or a scout goes sniper and one of the soldiers goes scout (generally the pocket cause shotgun aim transfers somewhat to scout hitscan)
driftaroamer mains usually have a high sens so they BLOW at sniper
pretty sure thaigrr uses a crazy high sens and he's kinda nuts at sniper... (maybe he's the exception that proves the rule)