Yes Yes Yes I completely agree with this
mostly. Neither Gondor, Rohan, nor Erebor should have buildable eagles. They already have good siege to deal with most of the
extra reasons Eagles are used for. Their main use should be against Nazgul's who can get a bit pesky in larger numbers. The only problem comes with Grond which can be devastating if you don't have enough stuff and an extra eagle can be a help with that(personally I don't like Grond at all its OP). This becomes even more difficult for Elves but they should have an Ent summon as well.
In the Powers Suggestions Thread I suggested Eagles summons for all Good Factions. Also, only one build able Eagle Gwahir for Elves as they lacked traditional siege for some of the more dangerous situations ala Grond. I also thought for them when the Eagle Summon Power is purchased and they have a Eagle's Nest built then it will have two slave Eagles who patrol around the size of the AI Base. This is again for problems that require large amounts of damage ala Grond. That way they would be no offensive threat, but would cover the problem of a huge nuisance which the Elves have no easy way of dealing with sans Spell Spam.
In the Powers I also suggested Ents for Elves and Rohan. A 5 Ent + Treebeard Summon for Rohan and a 4 Ent + Quickbeam for Elves. For Elves I thought it should be a bit different with Quickbeam. Lorewise he is the one with his mind made up and wanting to fight. Elves are the closest allies to which his people are in speaking terms. Once the Ents Power is purchased Quickbeam will auto-spawn out of the oldest Fortress. He will be like a regular hero save that when he dies he can't be bought back, but only comes back after a specific large amount of time as long as you possess a Fortress. Why a Ent Hero for Elves? Again its for the problem with siege that the Elves have especially against opponents with heavy entrenched siege themselves. It would make him useful, but not overpowered in that you would usually want him at home to protect your base from such problems. Furthermore both Ents Powers would be farther to the end of the Powers Tree.
The Giants I also suggested as a Power. It also allows the scrapping of the
Toilet Fissure as a build able structure. It summons the Fissure(perhaps reskinned?) from which 4-6 slave Giants emerge. They are lifetime and attack everything in the area even your own units. Lore-wise they were neutral and threw stones at whoever got close. The Giants would self heal when not in combat and after being killed take sometime to respawn. The Giants will continually respawn until the Fissure is destroyed, which would prevent respawn but any living Giants would still need killing. This might seem weak since you can't control them, but the fact that they respawn and you don't have to waste time microing them is a big advantage. Simply put them in an area you don't want to be easily attacked from and they should hold off most attacks and even larger ones for some time. Also, while attacking the front of an enemy base one could summon them to the back causing all sorts of havoc.
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Now the problem is two factions don't have very good siege. Moria and Lorien will be out their main form of siege attack.
For Moria I don't think something like the Troll stone throwers is fitting with the faction. Its basically a different looking catapult. Moria's biggest strength is that they are overall the most mobile faction and I think their siege should go along with that. I think one siege should be trolls built out of some troll cage or troll cave. The trolls should have that big spear thing that troll in Balin's Tomb tried to skewer Frodo with. It could do bonus damage against buildings and lots of AoE attack when used against units. The second should be the
Siege Bow . A ranged siege which is far more maneuverable than the catapults and can be built in larger numbers due to smaller CP cost. Another advantage it could have is that it fires faster and more accurately than regular siege, but does lower damage. I think this would also solve some of Moria's problems dealing with the Good Factions stronger units and heroes which could often level most of their army before much damage could be done to them. Especially with Giants gone that problem would start to get worse for Moria since they don't have many tank units.
Elves I think should have something completely different all together. I have heard from some people on the forum that think siege should be their weakness and I agree. Their powerful archers would make traditional siege far too easy. Anytime they come around with some siege and lots of archers the best counter would be spell spam for Evil factions. Getting units close is just so difficult with all the firepower they usually boast. Now realistically they should be able to build siege machines, but is that really their style to make machines? Second they only had a few successful sieges. In the first age these involved Human, Dwarf, and Ent allies. The only major siege success required the help of the Valar in the first age. The main Sieges in the Second Age required either the help of the Numenor or Arnor/Gondor. In the Third Age they have on siege against Dol Guldur which was felled by Galadriel's powers.
Elves I think should stick to magic. Now I know people don't like this idea, but Elves have always been known to have some secret powers/abilities what have you. I'm not talking about something serious here like spell book powers or hero powers. Something more subtle and simple. A unit that empowers other units around it to give bonus damage against buildings and perhaps even fire damage. They would simply cast a spell that during the duration gives a boost to all surrounding units. I think that is a fairly simple magic similar to how Gandalf easily heated Aragorn's blade in the movies. It would be a battalion with a few 4-5(including BC) units. I also think they should have healing powers as well perhaps similar to mobile wells or a over time spell like Athelas. I think this would allow Elves to have a very unique siege and deal with the problem of their overwhelming strength by giving them this one weakness. Unlike other factions they won't be able to sit back bombing away while enemy units rush in to stop them only to get mowed down by strong archers. They would now have to be very aggressive about their siege and rush into the attack. I think this fits their lore as well since they mostly liked to sit back in their hidden cities and only went on the attack with allies. For more traditional siege I think Galadriel should mostly deal with that I had some suggestions for her
here.