Well... a few days with 50 A4+ now and they really do suck.
I've got all 50 in Awesome Miner so I know when they stop mining and the stats aren't good.
If I mine on a pool that isn't 100% stable/efficient they can't handle it and where I assume the AntMiner D3s/S9s I have just deals with it and pick up where it left off the A4+ stops mining and restarts the mining process, losing you 5-10minutes of shares. NiceHash is a complete no-go too, they're can't handle it for some reason (vardiff?)
I'm using litecoinpool.org and this does appear to have helped stability. will update again in a few days.
Fixed difficulty is The thing with these. With some vardiff pools I've experienced similar behaviour as well. I'm currently mining DGB with 'multipool.us' via local stratum proxy and my measely 10 units keeps on rocking with no issues. Avg hashrate per unit (as reported by the pool side) are around 560-610MHs per unit. And I also tried NH after their "little haxx-problemo". Even tho using vardiff, it seemed to deliver pretty much what they "promised" or estimated.
Maybe the local stratum proxy (which I strongly suggest using, since you have such a huge number of miners) is the answer, or at least would help you out a bit?