I still believe it's more lack of execution, poor discipline and bad communication than scheme, but the scheme leaves plenty to be desired too IMO. 

 

Scheme issues:

The underneath zone is too easy to pick apart by the smarter QBs.

The outside CBs are left on an island when there's no pressure and there hasn't been enough pressure, so House is getting worked. 

Running this scheme seems to require having two playmakers at safety.  No evidence of that in Jax yet, so.....

 

Player/coaching issues:

Bad communication pre-snap

busted coverages - undefended receivers, TEs and RBs

Failure to bump or re-route/detour  receivers before releasing them into zone coverage

Not getting home with the pass rush or getting pressure fast enough to affect the play

Craptastic tackling in the open field 

 

EDIT:  Important to note that this scheme does seem to be easy to dice up for the better QBs.  Most of the team's wins have come against bad QBs.

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