Would the benefits of Defiance and Inner Beast not outweigh the extra cross class abilities from Marauder when soloing?

I can understand a DPS-build Marauder using Blood for Blood and Raging Strikes/Internal Release/Straight Shot/Invigorate though.

You won't need Quelling Strikes, Provoke, Flash, Convalescence or Mantra if soloing.

Protect? (you're soloing, so nobody else using it!)
Virus? (very handy!)
Stoneskin? (+10% Max HP Barrier)
Featherfoot (Dodge)
Keen Flurry? (Parry)
Second Wind? (Heal)
Feint? (Slow)
Haymaker? (Slow again)
Venomous Bite? (DoT)