I've always regarded "endgame" as an artificial construct. Sure each expansion has its most difficult PvE, but so what? MMORPGs offer a lot more than that. Naturally raiders view on-cycle EX+ as "endgame," but most players ignore it, demonstrating it's not some culmination of the content at all; simply optional content for those that enjoy it.
It's hard to estimate how much time I've spent in raids/trials/dungeons, but on cycle it's the bare minimum. I do the required MSQ dungeons and trials once. I don't need to grind for tomes because I don't need BiS for anything. In terms of time-on-task, I doubt I've spent more than 2% of my time on such content.
Theme park MMOs perpetuate this endgame myth, in part in a desperate attempt to make gearing up or skill trees remain relevant, while the other wing of the genre - sandbox MMOs - have always completely ignored it.