Yobit wallet is back online but currently still syncing at approx 4k blocks behind.
As for importing wallet.dat\keys from old wallet to new.....I am very surprised this isn't automated through a process already in Bitcoin core.
It is available in the rpccommand section of the console. The bat file is for batch import of 5+ priv keys at one time.... As an example for exchanges or mining pools that run windows and have hundreds of priv keys. Put them all in a file each on a separate line, and the .bat will import them all one by one.