And, yeah, everything is hot swappable on VAX.

Only the last generation or 2 of the highest end VAXen had any significant hot swap (VAX 9000/400 and later, which sold very poorly). The vast majority of VAX machines didn't. Even hot-swapping DSSI disks was at best iffy.

When someone whose been there talks about VAX 'high availability', they're usually talking about VAX/VMS clustering. Very cool and generally effective approach to the problem. That was one big issue with the end-game VAXen: clustering a couple of 6-figure mid-range machine was often considered a better solution than all-in on one 7- to 8-figure VAX 'mainframe'.

often require a service contract that includes a permanent on site tech.

I don't recall that being common with DEC service contracts. Most of the sites I know of that had dedicated DEC techs were either very large installs or had...other...drivers (e.g. tech had to have a TS clearance to work on the machines).