Nah. Especially something like agility. You need some verbals but fewer than you'd think. I use basically 3: Here (come closer/take the closer obstacle) Out: (Move out or take the obstacle further away from me), and mark (contact behavior). Otherwise it's pretty much 'do the thing you're pointed at.
You'd need more for obedience, maybe, but only in a 'general cues' kind of way. Given the number of deaf dogs competing - and frankly I own one of them - voice commands matter very, very little for effectiveness. It's ust more natural for us.
