We have a new driver from AMD the DAG for polaris is fixed in this situation?
NOT YET. They know the issue and can fix it, though.
How do we know that if claymore miner doesn't work well with new driver?
Because some people do not use claymore to overclock/underclock. They have their settings set in the bios. This is the only functionality broken with the latest driver is it not? Some people have tried the new driver and it didn't make a difference to their hashrate.