I have four YN-622Cs and three YN-568EX II flashes for my 5D3. zero issues -- the system doesn't miss a beat and has worked flawlessly.
The value proposition for third party flash equipment includes taking the risk of compatibility -- especially if you purchase from a no-name ebay snakester who has accumulated old inventory, does not have a return policy, and you don't establish compatibility commitments up front.
I wrote a review of the 568EX II flash and included in that review I made mention of how important it is to purchase from a reputable supplier such as thephotogadget.com. Before I ventured into the Chinese flash territory I confirmed that there was a return policy and that my compatibility needs were met, including optical slave functionality. Right now I wouldn't trust anyone except for thephotogadget.com
I have endured issues with Canon repair as well -- took them four times to get my 17-55 right and they displayed outright arrogance and unresponsiveness to their failures. I think they must have have employed a couple of monkeys just following instructions by rote, without any real knowledge and certainly no ownership to test for full functionality. my experience was almost enough to make me switch to nikon it was that horrible. In the end I got it fixed right and I'm still with Canon
Since it appears you are already financially committed repairing your 580EX I can only suggest to hold Canon's feet to the fire and test full optical master/slave capability, even if it means going to a camera shop to see if another used 580 will work with yours. Prove that it works with Canon before you test with third party stuff. Unfortunately Canon can't accept third party hardware as part of the measure of success.
When my 580EX died I decided to go with all Yongnuo hardware. What would have cost me nearly $2K in Canon cost me under $700.