A quick Summary, I may post more detailed insight regarding each unit or power.
A couple of suggestions regarding Isengard Faction. I have had the toughest battles,clashes and duels with End-Game fully upgraded Isengard faction. If player knows what he/she is doing ,in particular with the One-Ring they are indeed nigh invulnerable, Almost impossible to defeat even if you throw every single power,armies and heroes with their special abilities. Now before possibly common reply: " Do not allow them progress that far" Yes I partially agree,but the joy is to fight End game factions.
The Isengard has Unmatched Economy,Siege weapons and Infantry. They can counter any threat plus they do have strength in numbers as well.
Take for instance Imladris army, they are on paper the most powerful, Veterans of the Last Alliance for example or other units, but there are five of them only.
Isengard comes with 15, immense power,durability,protection against arrows,speed and other bonuses such is that Double armour from special building and Saruman with one ring and others.
For example. Uruk hai-Pikmen-Crossbows- all protected with shields,backed up with Balistae and wargs, captians nothing stands against them.With all upgrades and worst of all numbers.
There must be a difference between very challenging game-play and struggling against seemingly unstoppable overpowered force.
Fully upgraded Isengard in my sincere opinion has virtually no weakness at all. Their crossbowmen can penetrate with ease, Wargs are super fast and strong answer to other cavalry,archers or machines.
More than enough heroes, especially Scouts and Lurtz is a cunning combo when used properly. There are certain factions that stand zero chance vs Isengard, such is Rohan, their cavalry gets smashed ,hacked and cleaved in pieces, Pikeman are possibly best units to eradicate mounted units.
Powers as well. Mines,Additional temporary Army. You did incredibly well with Isengard overall. I truly appreciate your hard work, but judging from experience and overall outlook: The end game Isengard should be nerfed.
The only minor weakness I find is their heroes compared to others, they are not the most powerful tier, but more than enough to cause chaos compared with other features.
My suggestion: The reduction of their infantry size from 15-10 or reduction to Health pool,armour bonuses and damage potential.
Thanks kindly for reading