this seems to be problem, some people like me want the mod to be very hard on very hard settings, some people want a casual game on vh settings with extra buffs for the player and nerfs for the ai, and some people want it kept close to lore. IMO the slow development of settlements and expansion simulates the ongoing struggle and dispute for the same regions. Ive always had the impression that good guys are meant to be stretched thin, relying on good leadership to win the day. Also i always keep a general rule of thumb that if you take an enemy settlement of importance, they will be given buffs to help them.
A mod like RS2 is balanced for h/h which is meant to be harder then vh/vh settings, and house rules for this mod have to be followed in order to keep the benchmark of hardness up, but its beautifully done to give a feeling of amassing legions to stop an invasion. Ive always fount it hard to remain sporting with the ai, and that why i like TATW for its struggling ongoing war, since the ai and its buff don't don't care for how sporting you are and requires the player to use everything they can, ive been playing 3.1 and it seems a heck of alot easer....
Also im no lore expert, but when you think of middle earth in comparison to earth, military and technology wise, they haven't really advanced much throughout there timeline, being locked in a medieval state of period, humans from earth would having been using tiger tanks and automatic rifles by the same period. To have a city fully developed in 30 years, which is 130 turns, is asking to much, as the current development in cities seem balanced. londis (london) started as a roman settlement frontier, the romans were extremely good builders, but there building project would last for years and not seasons. If you ask for city development to be currently quicker then it is, your have settlements growing at a unrealistic rate.
Unless they bring in somthing that allow you to build settlers and send them to another settlement to boost population, there isn't housing boom in middle earth, like looking at housing prices at Osgiliath. it doesn't seem the right soloution is to start tweaking the speed of growth of settlements.
Use the same solution in the rome version fourth age
Bring in a settler unit that can be disbanded in a target region to boost numbers in another settlement, at a price of reducing population at which the settlers are built, and obvious cost for recruiting. This seem more accurate to me for the period too