Useless Pokemon? Who said that.
Wobbufet is a great Pokemon as it traps the opponents and forces them to atk, which is a problem if they don't have boosts.
If you can easly predict a move, for example scald from politoed you can easyly use mirror coat.
Unfortunally wobbufet can not do much else, it's movepool is small but workable, but it's great ability to take hits then hit back twice as hard is great.
Your strategy could work but I doubt it would survive 3 turns of possibly 6 moves on him.
I use him for a safe switch in, for example heatran is weak to the foes hippowdons e-quake you can switch into wobbufet take the hit, then encore so you can switch into a Pokemon that may be weak to its ice fang and yet resists ground.