I haven't watched all their games, but I watched the last one. Berlin intentionally sent their serve in Bratoev, that's why he is the only one that is receiving. This way they want him out of the attack.
For me the problem they had in some moments was with Caroll. He is left handed and they obviously had problems blocking him. He also has a nasty serve. And Berlin uses him a lot.
Have you read Mark Lebedew's blog? Very interesting reading http://markleb1.wordpress.com/ He even thanked me for Bulgaria - USSR 1980 Olympic final in one post