This thread is a good example of how complex the XC franchise is.
From my point of view, the whole thing depends on 1x key question
"is there enough demand for a 'fast' service from Newcastle/York to Birmingham/Sheffield/Derby?"
If there is, then 1ph should run via Doncaster and 1ph via Leeds. There is no real need to run the Leeds service onto the ECML, as this is better served by TPE. Similarly, if the purpose of the Doncaster service is be a fast SW/NE link, then it should not be calling at Chesterfield/Tamworth/Burton. The Leeds service could pick up these stops, essentially becoming a 'slow' Leeds-Birmingham.
If the demand isn't there, or the ~20 minutes saving doesn't make enough difference, then you might as well send both XC's via Leeds, which is clearly a bigger market than Doncaster. In this case, they would both run to Newcastle and might as well skip-stop some of the smaller towns.
So you have either:
Birmingham - Derby - Sheffield - Doncaster - York - Newcastle
Birmingham - Tamworth - Burton - Derby - Chesterfield - Sheffield - Wakefield - Leeds
or
Birmingham - Burton - Derby - Sheffield - Wakefield - Leeds - York - Darlington - Newcastle
Birmingham - Tamworth - Derby - Chesterfield - Sheffield - Leeds - York - Durham - Newcastle
I would lean towards the first option, but I change my mind everytime I consider it