Maybe they're stopping more free runs or getting beat less, that's definitely possible, but I've seen several plays with a free rusher, or a tackle gets smoked, and had it not been for Tua's processing, he'd have gotten wrecked. Why I don't think they're "better" is because of the time-to-pressure they're allowing. 2.1 seconds, compared to 2.3 seconds last year. Maybe some of that is the plan, I don't know, I'm just personally not comfortable with their level.
I'm not discounting some marginal improvement at some of the positions, I just want more. Until we know how sustainable Tua's time-to-throw is, over a season, we won't know how much it matters.