Lots of good discussion here, so I'll just jump right in
The counter for siege units could either be your own archers with silverthorns and longbows (Lorien archers with longbows or Caras Galadhon guardians have range similiar to that of most siege units), or Beornings or Lorien swordsmen with their speed ability. I agree it is more difficult to counter them without straight-up cavalry, but I wouldn't say it's impossible. Some have already said that catapults in general have too much health at the moment, maybe we could lower it a bit?
Catapults are meant to be effective against armies that are clumped tightly together, but they shouldn't be "sniping" single units and heroes. That is something we will adjust. One thing I'm unsure about is how good catapults should be against monsters and other catapults. The thing is that catapults are the only way a fortress might be able to defend itself against other catapults (and thus force the attacker to bring more that one single catapult or Ent to bring down a fully upgraded fortress because you need superior firepower). On the other hand, one could argue that a fortress shouldn't in fact have defenses against siege weapons. What do you guys think?
Ents are actually way better than trolls in every way except speed (more health, more damage, can be used as a catapult), so they should cost more CP. However, we could increase the flame damage they need to take before they start burning.
The Palace Guards are not meant to work the same way the Tower Guard does. Tower Guards are very much a special case, they're the ultimate unit for holding a defensive line: Good against cavalry and thanks to their shield wall they can take a lot of damage from other unit types as well. They are designed this way because Gondor is supposed to be one of the best factions at holding heavily defended lines. Lorien by design is not supposed to be able to do that as well as Gondor. That is why the Palace Guard is more specialized against cavalry. Note that they are actually significantly better at stopping cavalry than the Tower Guard: Their porcupine stops cavalry short immediately and their forged blades grant them twice the damage of Gondor's. As such an archer-focussed faction, I think Lorien is actually better served with a pike unit that is fully focussed on killing cavalry than an allrounder like the Tower Guard. And from what I've seen in that replay the Palace Guard did their job quite well: Whenever the Rohan player had his riders charge into your pikemen, they just got murdered.
So even if we replace the Porcupine formation, it would be with a specialized anti-cavalry ability, not a massive armor boost like the Tower Guard have. However, this would mean that Lorien would no longer have access to the Porcupine. The normal pikemen won't get it because we don't want to overload regular units with more than one active ability (their speed boost already requires more attention than many other abilities to be used well). I felt the Porcupine with its ability to stop even large groups of cavalry was something that Lorien really needed. If you think it could easily be removed from the faction, we could of course give the Palace Guard something else.
As for how Lorien should deal with heavily armored Tower Guards, it has already been mentioned that melee Galadhrim with forged blades (who have massively increased damage against other infantry) and human Beornings (who ignore heavy armor) are your best choices. If these turn out to NOT be effective against Tower Guards, we will have to adjust that.
The Star of Hope is actually a very strong power in my opinion. It's just the the Army of the Dead is likely the single best spell in the game, most don't compare that well to it (which I'm aware is a problem, but the Army is difficult to nerf while still keeping their feeling from the movie - but note that they take a while to appear and don't stay for long, so you can reduce your losses by running away). The rain might need a buff (as might the arrow volley), I'll look into that.
The thing about mass killer heroes is that they're usually not meant to be good against upgraded Tower Guards, but rather hordes of weak units like Orcs. Here, Galadriel excels and Legolas does quite well too (note that while he doesn't appear to have any AoE powers until the arrow rain, he attacks extremely quickly and thus can kill many weak units in a short time). But I agree that Lorien could use a hero that is specifically oriented towards killing groups of units, and many of Legolas' powers don't help very much with that. Maybe we could increase the AoE of his knife attacks and replace the archer training ability with something that's better suited against enemy units?
The Caras Galadhon Guards could use some more special powers, I agree with that and I'm currently brainstorming a few, so hopefully they'll pack some more punch in the next version
The idea is that they will be your go-to archers against less numerous, but heavily armored targets.