Remember that this isn't the first time they've made changes affecting the Clifton/Cotham/Redland services that have resulted in the Clifton side having a much higher frequency than the Cotham/Redland side.
A few years ago (can't remember when) there were far fewer 8s and 9s doing the full circle but there were extra buses (8a?) going Temple Meads - Clifton - Blackboy Hill only, with the 9a (?) doing the reverse.
And before that, (2001/2002?) there was the extra route 180 that ran Temple Meads - Clifton Village, giving Clifton far more buses than Cotham. For those that weren't around, the 180 ran via Victoria St not Bond St, and was introduced at the same time as the Class 180 Adelante trains on the London run; it was operated using the 1994 low floor Wright Pathfinder Dennis Lances originally in London, ODZ 8918 (fleet no. 8918) and her sisters.
Does Cotham/Redland need more than half-hourly? You can write off the University traffic as that is stitched up with the 16. There is the hourly 77 at the south end, and the half-hourly 72 at the north end. Not sure it really needs more?
I would say it definitely needs a service more than every half hour yes. These services can be uncomfortably over-crowded enough as it is at peak times and on Saturday afternoons/early evenings, and that's with the current frequency of every 12 minutes! And at these busy times, they're usually running late as well!
With this upcoming new timetable for the 9 now, there will be a gap of 45 minutes betweens services between 1630 and 1715. Busy Monday-Friday times when people want to get home from work or wherever. Absolute madness!
The hourly 77 only serves parts of Cotham and Redland. Whilst the half hourly 72 only serves Upper Redland. Not frequent enough for these areas really. And then there's the route from Temple Meads via Broadmead, Centre, Park Street, Queens Avenue, Elton Road, Woodland Road, Tyndall Avenue, St. Michaels Hill, Cotham Road, and Redland Road which will just have a service every half hour(or less!). So with the 9 being only every half hour, there would need to be a new service really to give extra frequency along this route.
And the 19 will be axed in September too.