I said 18/2 barb fighter before but pure Frenzied berserker THF horc barb may be it after thinking about it. The capstone can build up to +25 damage. Then there's +12 STR and +1 crit multiplier when you combine barb rage and death frenzy, trantrum cleave which gives +5W damage, +4W exhausting blow, +2W supreme cleave in addition to regular cleaves. If you have a healer strapped to you you could spam those attacks constantly. If we're talking highest DPS potential, pure barb has to be it. I don't see any other builds coming close to that.