I dont know what you mean by "heavily?" Also, the salt that you are using could also be the issue. Standard shaker salt, what we use while eating dinner, is smaller and you don't need or use that much when grilling or smoking food. I suggest you use a much coarser salt such as Kosher salt. I use this exclusively for outdoor cooking. I also suggest you balance the rub with pepper or some other addition.
I think if you do this for your next cook, you will have a much better experience.
Keep us posted