The killer instinct is the one consistent piece that's been missing since this whole doldrum period started for UT. Through the end of the Mack Brown era, through Strong and Herman and now Sark, they've alternated struggles with needing better talent, bad coaching, too many injuries, etc. Even when those things are on decent footing, the Longhorns teams of the aughts knew how to step on the throats of weaker teams, and not fold mentally when a team was of similar caliber and came looking for a fight.
Texas knows how to step on throats. But they have to relearn the joys of consistently keeping their boots there until the clock hits zero.