Looks like you are trying to run 6.1 packages on 6.2 kernel.
sysmerge was not needed almost surely this time after the upgrade. But have you done
pkg_add -u
Make sure that your /etc/installurl is not empty and has something like
https://openbsd.cs.toronto.edu/pub/OpenBSD
before running the command. You could also run pkg_delete -a after the upgrade to remove stale libraries.
I have upgraded all of mine 15 machines running OpenBSD to 6.2 two of which (my desktop and my laptop) run in GUI mode. I have not seeing anything crazy yet. As a matter of fact
WARNING: symbol(icudt58_dat) size mismatch, relink your program
https://marc.info/?l=openbsd-misc&m=149271724912565&w=2
has being fixed (it was affecting many programs not just slappasswd which I cared about.