Yes, good vets don't do those things anymore. However, terminology lesson:
There are different kinds of blistering. I think the one you're referring to is using some kind of caustic agent on a horse, wrapping, and then allowing all the nasty stuff--like the "bad humors" of medieval times--come out. And that is archaic. The one I know is using a combination of iodine and almond oil and injecting it in a localized area, such as for horses with locking stifle (luxation of the patella). It irritates the stretched ligament, causing scar tissue, which tightens it up and hopefully prevents the patella from slipping out of place again. I think it can be painful if you don't follow the aftercare closely, including hand-walking the horse, but I don't think it's agonizing, either, and is supposed to be pretty effective.