I'm not touching LBC, as the client source code is not available.
My machine is getting ~1 million keys per second with oclVanityGen. Not sure if it's not using my GPU or not picking optimal parameters.
Assuming that you are successful. What is the use of cracking keys when you are not scanning for balances. This is just another BIP39 social engineering clone tool. Yes BIP39 is a cool improvement but don't use it to fool the non-programmers.
I imagine people would check the balance for an address before trying to crack it. But like I said, it's main purpose is for the puzzle addresses, which have balances.
It's not social engineering anything. It's simply a brute-force tool.