I assume you're discussing the AC flight from YYZ. Time and equipment varies, but certainly since it's towards the end of the day if there is weather somewhere on the AC network out east it can be delayed. I don't think there's much of a priority to get this flight out on time since there are no connections on this side so having it depart late vs. a flight to Calgary will have less of an impact on the network. That means if there's a flight to Calgary or somewhere else scheduled around the same time with the same equipment that is running quite late, it's possible that AC substitutes the aircraft for this flight so as not to have people misconnect on that end.
Having said that, although it can be late, it's not generally an average of 2 hours type of thing.
https://flightaware....ACA1135/history
Of the last 6 flights, 4 were more or less on time, one was about an hour late, and the other was an hour and a half late or so.
Because the aircraft overnights here at this time of year, the flight out of Victoria is much more likely to depart on time.