your configuration looks fine, remember the Auto-tiering allows you to offer a pool on which you will now build volumes, the concept is very different from linear volumes.
You are not creating volumes directly on the SSD or SAS disk, but you create volumes on the pool which is built with a mix of SSD and SAS. the auto-tiering will take the responsabiility to move data between SSD and SAS itself accoridng to performance requires by your workload. keep in mind that we are talking about "Auto-Tiering"
i would advise you create another pool B, and balance data (volumes between ) those 2 pools (A,B) and avoid using only one pool.