Two 4 minute fights aren't anywhere near enough to determine something like uptime.
https://www.warcraftlogs.com/reports/p7 ... slate=true
for example has only a ~19% uptime for EEF. Honestly I think that person you linked with the EEF got really lucky but I don't know for certain.
According to simcraft, EEF has ~24% uptime and MoA has ~22.5% uptime (in my gear).
https://www.warcraftlogs.com/reports/F2 ... type=auras
My boss fights for an entire night of farm. I got ~27% uptime but MoA procs off of other players dying so unless no one is dying its going to have a higher uptime than simcraft. If you can find something like that for EEF I'm betting it'll be similar to simcraft.
If you really want to test it, go attack a target dummy for like 30-60 minutes (you don't have to actively attack it, just autoattack, making sure you don't auto-logout from going afk). That should give you a better idea. Since its RPPM, it doesn't really matter how many actions you do and the quick attack speed of our auto-attack should provide more than enough opportunities to proc it.