What do you mean blindly taking anyone? He's got Herbie Farnworth of all people unmarked on his inside shoulder, of course you commit to him. You're dreaming if you think DWZ sliding out to the wing would've saved that try. Damage was done.
Fuller commits Ali, now DWZ is two on one, and Fuller like any good ball player isn't pre-meditating the face ball, he's reacting to the picture the defence presents him. If he sees DWZ turn shoulders out to chase to the wing because he's picked a face ball like you suggest, Trai double pumps, plays short and puts Herbie through untouched. Ball playing 101.
If defence was as simple as old school union slide D systems, no one would ever score. There's things that edge could've done differently collectively before it got to that point but that's a different discussion and starts way further in than wing.
DWZ might be a shit defender but blaming him individually for collective failure is a long bow. And besides that one try, DWZ had nothing to do with Ali's shitty arm grabs that resulted in 4 missed tackles from 6 attempts.