In my opinion, if you're gonna do a high heat brisket, stay with the high heat, I always did 350. Just keep it in the foil. If you don't foil at high heat in your average smoker, it will char the outside. Then keep it in the foil (I think it's better that way for high heat briskets).
I started doing this for saving time. I'm now back to lower and slower because I like a good bark.