You probably need to work on your dodging then. Bubble is one of the "harder" quick moves to dodge because it is so slow and you have to attack a lot later than the actual animation starts. But I do agree that Poliwraths are incredible defenders. You should also know that Bubble having the slowest attack speed of all quick moves percentually suffers the least from the added 2-second cooldown when defending a gym, so Bubble/Hydro Pump combination actually has highest DPS for a gym defender (Note: Only moveset-wise, in practice it's not the highest DPS because it has lower stats than let's say Dragonite). It is very important to dodge effectively against Poliwrath. It is likely in top 3 Gym Defenders.
EDIT: Actually it appears that when defending Poliwrath indeed has higher DPS than Dragonite even despite the stats.
