I have experience with a RS/DP poliwarth as a blissey counter/prestiger. In that role she worked very well. However, in raids, although I include her in my lineup against tyranitar and lapris, but I've always joined a large enough group, that boss has always feinted before getting through the three machamps I put in front of her.
No way would I use a TM to change her to bubble. I'm not sure it would even be an improvement.