Simple addition to guild roster showing last time someone was online. "Last Online:6 Hours ago." And so on.
you can check to see if they're participating in the Daily Clan contest. Hitting Monsters, Gathering Resources from the realm, Training Troops, Upgrading Buildings and Doing Research will get them points in this. ALSO if a person has 0 points, they now also show up on the clan list as having 0, so scroll down to the bottom of the page and see all who have 0. Keep track of those guys and see how many days they have 0. If they don't meet your requirements, you will see. Way easier now than before. Just take down the list of those who aren't doing anything. If they are showing up with 0 points, they aren't active. Better than last activity date/time imho...just in case you have spies who join your clan to find out that info then leave with that info.