A frequent complaint on the forums is that rams are simply too powerful and can crush basically anything when massed. This patch reduces their attack damage by a factor 5, making them significantly less effective vs (organic) units, and gives them a 5× bonus attack vs structures, siege engines, and ships, keeping them effectively unchanged vs those.
Furthermore, it prioritizes defensive over other structures.
See also D2782 (make ram less effective) and D2508 (prevent ships and siege engines from attacking fields).