Not sure the 56 will ever be reliable in its current guise - very similar to the 21, in that the nature of the route (roadworks or not) is going to cause issues.
My own thoughts would be to split the service in someway.
Newcastle - Concord - express to Sunderland via A1231, Waterview Park/Fire Bridge HQ roundabout and then normal route from Southwick.
Concord - Sunderland on current frequency.
Should be doable without changing the fleet about too much.
Not sure about timings, someone may be able to work those out.
RE: Go North East Service Suggestions
'Illegitimis non carborundum'