Does your butt lack flavor with rub?

Nope. In fact, sometimes my butt has added flavors if I don't rub it first.

I tend to apply a rub, but, things are getting simpler and simpler. I don't inject either. I will do an add in of the juices and even a vinegar type sauce if that is the style I am looking for.

Did about and 8 pounder yesterday. Injected w/ a Dr. Pepper mixture I made (Dr. Pepper, woosty, country bob's sauce, brown sugar, rub, lemon pepper...add a little water if it needs thinned out some). Rubbed it with S&M Sweet Seduction. Put it in a pan at 165 to catch the juices, put the juices through the fat separator, pulled and added the juices back in...best I've made to date!

I've never marinaded a butt. I like the injection results better, but nothing wrong with marinading if you have the time to let it sit.