I've been experimenting with pot roast on the grill for a while now - both top round and chuck roasts. (Bottom round is just a bit too tough to cook dry, even lo & slo!) I cook them like a brisket - to an IT of 210F. Usually injected with Butchers Brisket injection. Outside rub has varied; I've done Sucklebusters Hoochy Mama, Oak Ridge Black Ops, and Dizzy Pig Raising the Steaks/Red Eye Express. All have been very good. Serious beefy flavor. Has become a house fav. Only reason for me to do a brisket anymore is for Burnt Ends.
My philosophy is - If the meat comes out a bit on the dry side, that's why we invented gravy!! My go-to is to saute onions and mushrooms until just brown, add a little AP flour, cook slightly, add beef stock with some Herbs de Provence, reduce until just about thickened, then finish with a nice dollop of veal demi-glace, S&P to taste. Doesn't get much better than that!