Lock out is to heavy handed
DPS queues can take a while & getting locked out for half an hour just cause you had to go afk is insane, SE if you want to fix a problem don't do it by making more.
Editing to respond to some of the posts
so I've seen a lot of people responding with the point of how can you miss for AFK 3 times in a day, but that was really just an oversimplified example so lets try a slightly different one
lets say a member of you FC has their tank drop mid dungeon & 2 people queue to help, unless one them runs a dungeon they had no intention of running in the first place, there's strike one
now lets add forgot to clear there duty finder & queued for the wrong thing, there's strike 2
& lets finish with your queues taking forever & you need to run to the restroom & it pops when your away, there's strike 3
^examples only & there's 101 more where they came from of decent reasons to get a strike
my only point is that 3 strikes over the course of a full day is easier then it sounds, i think if it was 3 strikes in 1-2 hours instead it would serve the same purpose without being overly harsh to the general population