I actually prefer using this card with Messenger of the King over using his hero version. This is similar to how (MotK) Legolas is often better than Legolas. As far as an ally, he obviously fits into Noldor decks and can become cheaper through To the Sea, to the Sea!. Stand and Fight can also be used to buy him from the discard pile after someone like Arwen Undómiel discards him. In addition to Noldor, he fits well with Legolas. His high amount of hit points makes him a great archery soaker. Overall, he is pretty solid.

Galdor is one of my favorite Noldor allies. He's not super flashy: his stats are okay, especially compared to allies like Glorfindel, Guardian of Rivendell, or Gildor Inglorion; he's somewhat expensive; and he simply isn't a key card to get into play as soon as possible. But his ability fits so nicely with Noldor decks, and it ends up being quite effective.

Noldor feature three heroes who can make easy use of Galdor's ability. With only Círdan the Shipwright, you discard due to his forced effect, and Galdor can thus draw you another card during the resource phase. With Erestor, if you have any cards in hand at the end of the round, then his forced discard will allow you to draw another, leaving you with five cards after drawing during the resource phase. And with Arwen Undómiel, you can discard a card, gain a resource, and draw a card from Galdor. This latter combo is especially potent with Elven-light: you can discard Elven-light for a resource, draw a card from Galdor, then play Elven-light, likely with the resource you gained for discarding it, drawing you two extra cards every round at a cost of zero resources.

The Noldor archetype has a ton of ways to use these cards. Accelerate your boardstate with To the Sea, to the Sea!, heal your characters with Imladris Caregivers, put Elven Jewelers into play, discard cards to be able to play a Guardian of Rivendell, ready Glorfindel, keep a Lindon Navigator in play, or even play the cards you drew.

So if you're using Galdor, it will be in a deck where he gets you one extra card draw every round. We can compare him to an old core staple, Gléowine, who costs 2 to give someone at the table one extra card per round. If we then say that Galdor's ability is thus worth 2 resources on its own, that leaves us paying 2 resources for a 2/2/1/4 ally, which is pretty close to just as good a cost-to-stat ratio as Quickbeam. But we're not really going to pay 4 resources when we have Arwen Undómiel, Erestor, and To the Sea, to the Sea! No, he can be pretty easily discounted to 1 resource, at which point he accelerates your boardstate, provides questing or attacking (or both if Narya is in play), and can be boosted by Lords of the Eldar. Extremely solid, even if a Noldor deck already has so much going for it that he's not a key card.

Beyond the good combos mentioned above, he also goes great with Legolas, and if you want to build something janky with the early Noldor cards Watcher of the Bruinen or Trollshaw Scout, Galdor's your man. Er, elf. Galdor's your elf.