does that mean alderwood will be able to support 4 groups? elmwood another 4 groups? coombe tor another 4 groups? isn't that a lot of groups for each map? shouldn't those be a rare commodity?
Also for being viable you shouldn't take too long to a new one after finishing the last one.
So even though a zone can sustain up to four groups it doesn't mean that this would be very efficient.
If your group has the zone to themselves then it will probably take about 2 minutes to find a new one but with four groups it is hard to calculate how much longer it will take them.
My guess would be something along up 10 to 20 minutes.
Additionally a gank group would now have to find and then check each and every dungeon for possible targets.