And perhaps more importantly, aren’t some of the station dwells e.g. Derby and Sheffield as long as 7-8 minutes? Improved pathing would help.
Some are long dwells, but (as we've discussed before on here) many are long because XC services are moving from one line to another and need to wait for a good path.
For example, if we talk about the "proper" XC service from Birmingham to Newcastle, the half hourly Voyager, it needs to fit around the half hourly Nottingham-bound Turbostar that leaves New Street at xx19 and xx49 that take maybe seven minutes longer to get as far as Derby. They arrive in Derby at roughly xx08 and xx40, so you might say that the Voyagers shouldn't arrive before xx15 and xx45, have a three minute dwell and be ready to leave at xx18 and xx48?
At Derby, there's two EMT Meridians to Sheffield, leaving at xx09 and xx28 (due to the lopsided nature of the EMT timetable). They take the same time to get to Sheffield as the Voyagers, so there's no time differential to worry about.
But at Sheffield you have four other services per hour to Doncaster, two slow ones at xx05 and xx30 which take forty minutes and two fast ones at xx10 and xx24 which take under half an hour. Yes, the four non-XC services from Sheffield to Doncaster run within half an hour of each other - the timetable is a real mess, but that's the kind of thing that XC have to fit in around.
OR, there's the busy line from South Kirkby Junction to Leeds - a mixture of stoppers and InterCity - six trains an hour from Wakefield Westgate into Leeds. Then you get to Leeds and find yourself fighting for York paths between all of the TPE/ Northern services heading towards Micklefield.
Any improved pathing on one section of line might only end up with a ten minute wait at the next big junction (rather than a five minute wait at two junctions). And I'm ignoring randomly timed slow freight in the above examples.
The only saving grace here is that at least Voyagers can meet the current timetable. They are fast accelerating and reliable. 222s ought to be able to do it too. But HSTs would struggle - which is why the idea of "simply give XC some HSTs from GWR/VTEC" is a non-starter - you can't rip up the timetable and start again.
Until HS2 comes along (which will take Birmingham - Leeds down to *one* hour - half the current duration), I don't see much scope for speeding up XC - its just a case of throwing more coaches at it (albeit coaches capable of fast acceleration with a good top speed, which kind of restricts it to 222s for the short/medium term).