Not every off-peak bus will be busy as, yes, it's off-peak (that can even be said in peak times too). But the Blue CityGlider is the 2nd highest patronage route in Brisbane sitting at just over 3 million trips last financial year (see link below). This figure has grown substantially year on year for the past 5 years and is expected to continually rise due to the sheer number of apartments going up on both sides of the route.
There are also times where there are off-peak gaps between services of 15, even 20 mins (due to late running buses) obviously meaning that the following service will be very busy from the backlog of people. It all just depends on how many people are out at any one time.
Also, when the Metro comes online in 2023 (hopefully), it will be spitting more people out at the Cultural Centre and KGS where people need to change onto the Blue CG who are travelling north-south down the city spine (Adelaide St) to places like the valley and blocks further north of Albert St. It is and will continue to be one of Brisbane's high profile routes and needs to have buses running on it with a high capacity and ability to turn over high numbers of people.
Patronage: https://railbotforum.org/mbs/index.php? ... #msg227821
Is it possible to have some double-deckers?