Barth has more use than Wendy (he can weaken enemies considerably), but it isn't saying much. He's basically all HP (100% growth), STR (60% growth), DEF (40% growth), and nothing else. His SPD base is very poor, and his growth isn't gonna help much, which is 20%.
2.5/10, -.5 since I don't like his character at all. 2/10.