Depending on the type of smoker you are using, the temp at the door (gauge) could be 50 degrees off from the center of the rack. I have some minor leakes around the bottom of my door on my RF and the door gauges will be showing right around 200, when my Maverick is showing 240-250 in the center of the bottom grate.
As far as dry, crusty, but tender ribs, it could be from too high temps, less meaty ribs, could be that last hour back on the smoker to finish the 2-2-1 method, for the most part, maybe only a half hour is needed for that stage. Might have built up that crust during that stage.
Goinforbroke, well done on the post on how to cook ribs (gonna throw you some points for that post!). I agree with you completely. Rib cooks have specific time frames and signs that I am looking for during the cook. Cooking comps I mainly cook spares, so it's a modified 3-2-1. I look for pull back on the meat from the bones, but for the most part at the 3 hour mark at 250, I have what I'm looking for as far as color and the pull back everytime, so I foil at the 3 hour mark, now when it come to the 2 stage, I do the toothpick test, if I'm at a comp, it's cook 'em until they nearly fall off the bone (you got to cook them tender here in Texas, they only take samples with a plastic fork and knife) if I'm at home, it's usually at the 1 1/2 hour mark, the toothpick should easily slide through the meat with little resistance, when this happens, they are ready for a light glaze or sauce, then back on usually only for a half hour or so.