Oh, it could be exciting. Especially when one came back with no rider and the saddle on its side, then they fix it and beckon you over.I imagine the primary reason the mules were E ticket was because between the number of cast needed and the mules, it was quite an expensive attraction to run.
Of course, I'm sure it was a lot more exciting to go on a pack mule ride in the early decades of Disneyland than it sounds to me personally right now.