The new update (Version 26.2.0, Beta) marks people offline immediately (estimated max. one minute after being online). The "online"-Filter doesn't show anyone being active anymore, not everyone has the time nor motivation to use the app all the time (maybe that's what this 'new function' is supposed to be leading us to).
10 Minutes were perfect for making the grid seem alive.
I'd be fine with 5 mins too but this is too much.
I wouldn't like for people to know exactly from when to when I'm online.

Why do you keep taking away functions that worked fine? You should focus on bringing new ones to the app or making the ones you have work better. A grid that doesn't need to be refreshed manually would be great, with proper sorting-animations etc.