No, the 15% fighter haste is being over-hyped. People haven't yet tried out the changes to THF, the 10% increase to glancing blow and 5% proc for specials ON EVERY SINGLE HIT, will more then make up for the DPS loss. 6 casts at 20 seconds is 2 minutes of 15% DPS increase. Its a tough call I would say it's a wash....BUT throw in the extra strength and rage/DR/etc. and I'm leaning toward pure barb. Plus don't forget you're going to have to re-activate this EVERY 20 seconds, there is a slight pause during activation processes and thus losses of DPS.
HOWEVER, stunning blow is the determining factor. Free feat, stun blow (the +1 DC is meaningless to a Horc Barb) is a pretty big incentive. BUT its not like you can forgo toughness for Stun Blow on a pure Barb (it would be about 60 pt HP difference between a pure and 18/2..which translates into ...who cares?)