Smoked a brisket that was edible but not great. What would you do differently?
From what I can tell you're generally on the right track here. From what you've said, there are probably just a few issues.


tough/dry/rough. Believe it or not not cooking long enough could be the problem here. You want your brisket to get in that 190-200 range, this will cause the connective tissue to break down and make it very nice. The other possibility here (and you didn't say so we don't know), is that brisket can be very tough if it's not cut properly. You need to cut the flat across the grain for it to be tender as it's a very long muscle.
Lack of a smoke ring. This is what we call the pink ring around the outer bit of the meat. You don't want the inside to be pink, you want the outside to have a pink ring around it. This can be unpredictable in formation and depends on a lot of things. If you liked how much smoke flavor your meat had, I wouldn't change anything, but if you wanted more smoke, try to either put in more wood chips at the start, or put them in dry (careful though, you don't want them to burn, but wetting them really just slows the burn time). From what I've read, the smoke ring forms early, so the first hour or so is the important part here.
Foil. This is hotly debated in the BBQ world. I only foil if I need to hold my meat for a period of time (if I mistime and finish early I'll wrap it up, drop it in a foam cooler with towls), but a lot of people swear by it for producing juicier meat. Totally up to you, experiment here. 


Lastly, a few bits of advice (I've done a couple of briskets now, all on charcoal though). Don't bother to sear the meat, let your smoker take care of the whole cook. Do that, make sure you get your meat up to temp (brisket is hard to tell without a thermometer as it doesn't have a bone you can check, so go get an instant read one, they aren't too expensive). As far as the dry rub goes, that's a matter of taste, a lot of folks put it on the night before, but the meat gets plenty of flavor just applying it right before you put it on.