When you are 1-3 and you just want to stay in city and militia will encourage you, belive me If i will enter with 14 other armed guys militia won't help you. Of course if it is default militia not added mercs v 400hp's. So If your point is to stay in city only for lulz and only if someone will came than try to run away and regroup, so what's the point of staying there ?
There are vast ammount of people who think controlling town isn't just about pvp and having name in pip boy. As a pvp player and hinkley activist you might never understand this. But honestly some players just want to hang out in towns, just like they do in ncr. Or participate in activity that the town offers, such as mining, trading and quests, which are limited at the moment. In unsafe towns there is a benefit of creating your own rules and applying them, which can't be done in npc controlled safe towns.
Controling the town should means that you ve got a good amount of well equiped players who can really defend that city.
It should also mean that you actually offer the city your presence and decide what will happen to random visitors. Can't demand a group of armed and drugged guys to stand there forever, but at least one or few guys who upholds the rules agreed by the controlling group. Those guys need to be encouraged to stay inside, which militia is good at. If it seems that players will prefer to kill everyone, then they should be encouraged not to do so. Like the "mining for influence" feature tries to do.
Not some bluesuit sneaker added to faction base standing with assault rifle and shooting everyone using militians or you and your 3 other friends want to chat in city It s TC not NCR...
Who are you to tell how people are meant to spend their time in their town?
And if your suggestion is to make militia less stronger it wont' change nothing. Some other 3 guys if they will try hurt your 3 friends standing with 20militians, still they have no chance when its 10 militians => swarm gang will come still no difference between 10 or 20 npcs. Problem is with miltia's exploits and possibility to adding them when other same powerfull gang is gaining influence in town in same time.
Like Rascal said, max 8 militians, preferrably weaker too. Add some more respawn time and disallow adding militia when enemies are in town.