Sorry you had such a poor experience. I'm afraid the non-AVOD 343s assigned to the Vancouver route are indeed the short straw in the LHR fleet.
The VS 13-hour seat request thing is a bit odd and I feel for you getting caught out by it.
As for the luggage -- that is really poor (but also probably just very bad luck)
I hope you get an apology, at least.
If it's any consolation (and it won't be), they can be brilliant, but I will certainly admit there are inconsistencies...