It's possible, and the time-remaining portion is good idea. I'd join an AK that had more than 90 minutes left and appeared to be demon wall. I wouldn't join one with less than 70.

The rest isn't a good idea for 2 reasons.

1.) It divides a low-population pool too far.
2.) We've all seen the person farming one boss, or one portion of the map for drops. You want something off the second boss, you join a 1/3 group, kill it, and disband. See the problem?