Some blends smoke hotter than others. Some times conditions (wind) cause the pipe to smoke hot. Try sipping, but even then you may find that they smoke hot. I was smoking some C&D Haunted Bookshop in a RobRoy the other day, and noticed that HB smokes hot in this particular cob, Plus the walls to certain cobs are thinner than a briar or other cobs. The MM Diplomat has thick walls and smokes cooler. Also My 5Star McArthur has thick walls and doesn't smoke hot. When it gets hot take a break and let it cool down. I love my cobs, and find that I get better flavor from them than my Briars.
Like Deathmetal said, try Carter Hall in the cob and see if it still smokes hot. Plus, smoking slow isn't the same as sipping. It took me awhile to figure that out. You can smoke slow and still be taking big drags(that's a no-no, those drags will water down the flavor) which will cause the pipe to still get hot. Chasing embers(Big Nod) is the goal, not smoking a chimney.