I know you aren't keen on groups but if you are using one course with lots of students and lots of teachers, then if you prevent the default teacher role from being able to access the other groups and set the course and all activities to separate groups ,and prevent students from viewing each others' profiles (See docs here), would that help at all?
Also, here is a blog post from Moodle Partner How to Moodle: http://www.howtomoodle.com/blog/moodle-tips-moodle-multi-tenancy/
(And by the way - with ref to your tweets -there's nothing "dreaded" about iomad ;) )