I used my bandsaw the same way you did. The I used a painter's multi-tool to open the power supply. I'm going to have to say that this is the easiest way ever. I take it a lot of the negative comments and thumbs down are because you actually showed some mistakes which happen in the real world all the time. But, from now on this is the way I'm going to open these - I didn't need the hammer. I say good job on showing the brute force method!
The easy way is to stick it into a 4" vice and then slowly compress half of the adapter housing near the seam until the glue cracks loose. It helps if you heat it up with a heat gun first around the seam as well, but not too hot to deform the casing.
I just opened one very easily using a sharp chisel and a small hammer. Probably not all of them are going to open as easily as the one I just did, but you could always try it before breaking out the bigger (and potentially more dangerous) guns.
You can do the same thing with a rubber mallet. You hit it on each sides on the joint going around it until it gives. No band saw needs to be harmed :P
Or redoing it properly with both hands. Also, if you go down that much in a wall wart you will break them. You should only go in as thick as the plastic.