In retrospect, I like the fact that the end battles with the Crimson King and Mordred were somewhat anticlimactic. It's like Roland says several times, it all comes down to just a few minutes or seconds in battle, all the long preparation. Even Mordred recognizes this, he wants to kill Roland as quickly as possible in a surprise attack, no messing around. Some drawn out karate fight with the CK where all seems lost until the very last second would be cliche and boring.
I also think that Roland has fought the CK before, on previous trips, and using Patrick was part of the "right" way of finishing the quest.
I think Roland did save the tower, and it happened pretty much similar to what we've read. All of the ka-tet have been through this before. Roland has become like Flagg, quasi immortal and his repeating the cycle is not a punishment, but rather a reward. He gets to go back and have the chance to not make the same mistakes and cause pain and suffering to those around him. This time he has the horn. This time he might not drop Jake. Susan might be alive this time around. The ka-tet might not break.
One of SK's better endings I think, thought provoking and satisfying, and I don't regret any of the journey through this series.