I am looking to level a 2nd toon on hardcore and I really like the fact that at cruel difficulty on titan I can just one shot the bosses and don't have to worry about mechanics. Is there another class that can do this while leveling?

Gas arrow with the Radiant Grief helmet is very good for twink leveling. Just remember to upgrade your bow every so often. Level 28 then advanced base. I've leveled 3 characters (ranger, warrior, mercenary) with this all past campaign and 4th trial done.