Pretty sure ive solo capped towns before... however the order you take the flags/kill the guards is important... make sure to take the flag with 4 guards last and the flag with no guards first
Cropsford was "buffed" in order to offset the fact that DC (Winter's) and AD (Carmala) were given outposts on their borders whereas Harlun's is in the middle of nowhere.
It's stupid that the map isn't balanced like this whether it's with 6 towns or with 3 towns/3 outposts all the same distance behind each faction's emp keeps.