The reason behind the long layovers in Toronto: we only have 3 flights a week as the Canadian Government is not willing to give more slots for Emirates. So, Canadians now need a visa to visit the UAE.
The reason for some of the long Hong-Kongs: operational. Meaning aircraft changes. Those flights didn't go on the A380 every day but the crew either trained on the A380 OR the other aircraft types (main fleet).
No, most of the new ones are NOT prepared for the job. (Not only the job but being far from the family, living in Dubai, working in a multicultural environment.) That's the reason for the high turnover rate. No, most of the new ones don't do much research and know about the short layovers. It's OK: they either get used to it or resign in a year. You can always call sick if you are tired. Maybe you won't get your upgrade due to the high number of sick days but some people don't care about it. It's OK: better for the mature and hard working people who are physically and mentally stronger and more commited.