I've ran flex tons of times and I've never had to use a 3rd party add-on to do so. If you don't like the requirement someone has on their flex, start your own run. You can fill to the min of 10 rather quickly during peak hours, even faster with OpenRaid.us.
Also, while you spent 2-3 hours doing dailies and getting your secrets, I spent the same amount of time and cleared the whole place on flex.