Afking is promoted by the absence of a proper matchmaking system.
The absence of a proper matchmaking system might be due to the low player base. This doesn't justify the current situation though.
When a 5 man group of experienced players (possibly with teamspeak) is matched vs an unorganized group (of possibly noobs), something has to be done. You can't blame people for going afk in a stomp. It's bad design to force players to sit through an unpleasant experience by punishing them for afking, when you don't try to reduce the occurence of those unpleasant experiences at the same time.
When matchmaking isn't an option as stated above, other options must be looked for to temporarily deal with this problem.
This could be done by showing enemy player names in the lobby, so you can dodge premades. If those premades have trouble finding opponents then, it's fine, coz it's their choice after all.
Or you could just reduce max group size to 2 or 3 (for a few friends or a noob + mentor), or remove group queue all together, because 5 man premade vs rdm is not fair at all. There's still custom for proper premade vs premade matches.
These "solutions" are ofc only meant to be temporarily as long as no matchmaking is existent, a band-aid is thoroughly needed in any way.