If you want to use Poliwrath, it needs to be a set that won't be outclassed. In other words, it should be doing something that other Pokémon can't do better. In Poliwrath's case, it is a great Pokémon to use Substitute + Focus Punch.
Martini, Ehh, Suicune does the same thing except better. It doesn't have a water immunity, but it has 100/115/100 (or something) defenses, and has Roar which will hit through substitute.