BGHs great value comes from Dr.Boom. Without DR.Boom the average number of 7+attack minions on a deck may not be as high to justify BGH a spot. Same goes for mindcontrol tech. They have other uses ofc but Dr.Boom made them much powerful.
About Dr.Boom;
The counter cards BGH,Mind control Tech have been the most popular they have been after GvG release. Even with counter cards being this widely used Dr.Boom is in most decks. That means Dr.Boom is OP.
A good card appears in most decks. People start to counter it. Then it fades back to a reasonable spot. Thats how meta shifts. Except for Dr.Boom.