I think one way we can make the bowler more effective is to have the bowler throw his boulder and when it lands, it fragments into 3 or 4 smaller rock pieces that do slightly lower damage than the original boulder (say 30% for 3 pieces or 25% for 4 pieces). This way the bowler could be the one troop in the game that can hit multiple buildings at the same time. Each boulder bounce of course would still do splash damage which might make it a more attractive option on defense.
