Hi,
currently in the tasks there is no practical sorting by priority.
The click on priority column gives you either:
1. high priority
2. rand("medium/regular priority" or "no priority"
3. low priority
or the other way around. It does not differntiate between "regular priority" and "no priority" tasks.
Please consider implementing "regular priority" tasks to be on the second place, and "no priority" on last place. That is the implementation how tasks.org sorts the data from caldav tasks.