Having been working at Busch Gardens since last year and going pretty regularly all my life, I know that operations at this time of year are very off and on. At log flume (where I am), during the weekdays, we almost never run both channels. We just don't expect that many people. Even if the queue gets very lengthy in the middle of the day, it doesn't make sense to add boats as that would take up even more time.
Now speaking as a guest of the park, I have only ever seen Montu run one train once in my life. Kumba runs one train all the time. Therefore even though it's my favourite coaster, I rarely ever go back there because I know the queue will be horrendous. SheiKra usually is pretty good about keeping the trains from stacking, even if they only run one station.
Hope you guys have a better time the next time you guys come!
Oh and RiP Gwazi.