After my last run, I disagree. While Stoutland can't guarantee it will be faster than the opponent, 80 Base Speed with average Speed IVs and a whole game's worth of Speed EVs (Speed EVs are extremely common in-game) means that you'll be outspeeding a fair amount of stuff, even later in the game. Combine that with those solid defenses (especially with Intimidate), and you'll have a reasonable chance to land some Returns before getting taken out.
A strong STAB Giga Impact can't be discounted, either. Stoutland is bulky enough to switch into most attacks, and if Stoutland is either faster than the target or can survive a second attack you can put the enemy in a whole world of hurt. Worst case scenario, Stoutland is the best sacrifice switch available pre-credits, since you'll always get a free growl out of him. He does a solid job buying time to heal up, too.
Honestly, the only point in my last run where Stoutland wasn't a productive member of the team was against the Elite 4, and that's largely because Scrafty was too busy wiping the floor with everything to bother using him.