I have never even seen the move Embargo used once. Obviously there will be counters, and things that make them close to useless. However, if those same things are done to their evo's then their evo's will be useless as well. Gimmicks are also poor examples. Even without evolution stone Chansey has massive HP and pretty good SpD, and Dusclops' defenses are only 9 points or so less than his evo. I don't see how that would make them completely useless. I don't know about using Hippopatos as the Pokemon still need good HP to have the same overall bulk. Porygon2, in my opinion, is probably one of the best Evolution Stone users. He already had pretty good defenses before and had 374 HP which isn't bad at all, so he's really benefited from this.