Does the tackling need to be better than it was last yr- yes, without question
Would it be nice to get more turnovers- yes, without question
But gauging whether a defense is good or bad based on hard hits isnt all that telling either. As you even mentioned in your OP, the Cardinals had a number of big hits, but their defense was absolutely putrid and they gave up tons of pts, yds and big plays. The Cowboys championship teams certainly didnt have a "menacing" defense, but they were sound from a fundamental standpoint and played exceptionally well as a unit. We had a couple f "big" hitters, but I doubt anyone would confuse them with being as intimidating as something like the 84-86 Bears defenses. At the end of the day though that didnt matter though did it? Those Cowboy teams won 3 championships in 4yrs, the Bears managed 1.
Thats why it doesnt matter as long as the results are good.