I agree with this. Brutal AI has kind of 2 states in Edain according to my experience:
1st - Its so strong that they destroy me in several minutes, economically its impossible to hold them (especially map Nurn).
2nd - Its pathetic (majority of other maps).
Today, I me and my friend were playing 2 on 2 game. We always play against Brutal, because lower difficulties are too easy. I was Isengard, my friend was Gondor, and we had 1x Brutal Gondor and 1x Brutal Mordor against us. The starting positions were Castles.
At the start of the fight, they spammed a lot of unupgraded units. We easily defeated all their attacks just by having towers, especially my friend playing Gondor had no problem at all, because AI just flooded the gate and totally ignored towers / walls.
In several minutes, we were able to go offensive. I Took one camp with 3 building spots, I builded 2 towers and putted Crossbowmen into each tower. From that point, enemy was not a thread anymore. They could not bring those 2 towers down at all, they didnt even try to bombard them. They just kept sending units and kept dying to arrows.
My Gondor friend had similar experience, his Castle towers destroyed everything.
When we went offensive, AI didnt even bother to build defensive structures.
We played many other maps. On majority of them, its similar and Brutal AI is weak. In some, especially Nurn, Ai is very powerful and starts to flood your base with fully upgraded units after several minutes of play. its very hard / next to impossible to defend yourself against it.
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I think the main problem that Ai has are the unit upgrades - especially ranged unit upgrades like flaming arrows. It is a problem in both ways --
If the AI is too strong and start to flood your base with fully upgraded units early, you lose, because you cannot possibly have enough money to upg your units, and normal units dont stand any chance against upg units.
If the AI is weaker and dumber, you can destroy them with a few groups of upgraded archers. 4 groups of fully upgraded archers can hold the enemy armies forever.
My suggestion would be making upgrades cheaper and less powerful. That would solve both sides of the problem.
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Very often, the AI plays like dumbie - no unit upgrades, no siege weapons, no defenses. It looks like AI lacks resources to buy / build stuff. AIs are not building bases, not buying heroes, not recruiting the best units.
Brutal AI should be Brutal. There are 3 other difficulties for easier gameplay. Of course, I am not asking for unwinable battles, but current Brutal AI is just very easy to beat. We, humans, have advantage of clever usage of heroes, spells, of strategy. AI should have way more recources to make up for that.
There was a mod called Elven Alliance that I played for years. The hardest AI was tuned greatly there, Ai was building, making siege weapons, had fully upgraded armies and flooded you with units.
I hope this mod will eventually get same difficult AI.