It sounds like you are already aware that the foiling prevented the bark from firming up on those smokes.
My main suggestion would be to make sure you use a binder of some type. I typically use plain old yellow mustard or canola oil. This will help make your bark more substantial and not impart any other flavor.
For pork butts, smoking at 235 will help firm up your bark. I still prefer 225 for brisket, though. I still get great chewy bark when smoking at 225. But, bumping to 235 will make the bark even chewier without any loss in moisture in your meat.
I would also skip the step of bringing the meat to room temp. Our motto here is cold meat into a cold smoker. Do not preheat your smoker or let your meat come to room temp. This allows your meat to absorb as much smoke as possible before the internal temp hits 140, at which point the meat pretty much stops absorbing the smoke and instead it just builds up on the outside of the meat and can become bitter. This may help with the bark process too.
I have smoked butts and briskets brined and not brined. I have an injector, but I am guilty of not using it very often because I get pretty darn good results with only the brine. Up until about a month ago, I had not smoked a Boston Butt unbrined for 2+ years. But, I had a last-minute Boston Butt smoke that I did with a simple mustard binder, my favorite rub, and into the cold smoker at 225 until the butt hit 190. The results with my standard Sam's Club pork butts that are very consistent in quality, were noticeably sub par from my brined butts. If you haven't tried brining, I would strongly encourage you to give it a shot. I don't think it really had anything to do with the bark issue. But is just a great preparation tip that can make a huge impact.
I usually use a disposable tin mini-loaf pan filled with water or apple juice placed on the bottom of my smoker floor resting right up against the smoke box. But, if you want to really maximize your bark, skipping the water pan may be a good idea.
This is what I can think of for now. We'll see what suggestions others have. All I can say is that I have never had a problem with my bark. My only problem is that I have teenage boys that love it as much as I do and I have to fight them off with the bear paws to ensure that some bark gets mixed in with the pulled pork.