Warriors don't need "whacky Dark Side stuff". They just need the Force to get to their victim and to shove a lightsaber through their heart.
As far as influence goes, Marr, Malgus and the Wrath aren't the only influential Warriors. During both, planetary questlines, Warrior and Inquisitor-archetype NPCs, both hold relatively similar amounts of authority. The greater half of the Dark Council are Warriors - as seen during the Republic Corellia questline. So I wouldn't chalk up superior influence and authority solely to the Inquisitors.
You do realize that the game rules concerning classes only apply to the players themselves and to NPC's, it has no bearing whatsoever, right? Takes Baras' for instance...
Unless of course, you really want to be silly and assume this all suggests that class respec will be a reality further down the road.