Thanks for the feedback, I'll log an internal issue for consideration.
Don't forget, background processes (tasks) are designed to work in the background, they are designed to run when your community is open and available. Cron is the quickest, but depending on your knowledge you could also call the same path in a bash script if you wish. YMMV with that though.
What kind of background tasks do you have running, you shouldn't really have that many resource intensive tasks after an upgrade from 4.4. Although you do mention a 'conversion' so I'm not really sure if these are tasks from an upgrade, or tasks from a conversion from another software.