A jack of all trades maybe. It's not about being below average at any one of them, it's about being able to do all of them *at the same time.* He can get jango and energy boots and support your carry. Where a hero like Dazzle might do the same thing, Sven fulfills a very different role in team fights. Dazzle basically sits back and waits to shallow grave, otherwise not changing the fight much. Sven runs in with 300 damage swings and forces you to not ignore him.