It seems strange to me that no one is gushing praise for this card. First, it seems obvious this card was made for playing Outlands characters and is quite effective for doing so. For example, Hirluin the Fair can play Ethir Swordsman and draw a card from Lord of Morthond. This is great. Second, it is perhaps even more potent with Silvan tricks that are already quite powerful without this boost. Any mono-leadership deck is likely to be running three copies of the much-praised Steward of Gondor, whose resource generation has warped the entire game from day one. Let's say Thranduil becomes Steward of Gondor (thus gaining the Gondor trait) followed by Lord of Morthond. The Elvenking becomes recurring card draw in addition to its already useful function, Feigned Voices now replaces itself when Galion is replayed for free with Thranduil's combat ability, and Host of Galadhrim becomes the best card-draw event in the game in addition to its other benefits. I suppose one could even run both Outlands and Silvan in the same deck with Hirluin the Fair, Thranduil, and Celeborn leading the way to a full four-color army of "cantrip" allies?
One of my favourite cards. Traps in general deck styles to play and this card fills a pretty big gap in that deck. I want to point out that it's the sort of card that gets better against harder quests. The more threat on a trapped enemy, the more willpower he cotributes. I'm currently playing Helm's Deep where there's an assortment of 3 and 4 threat enemies, and this guy just rises to the occasion. How many other Allies can boast 2-4 willpower for 2 cost?
This card is spectacular for Grey Wanderer decks. Because he isn't unique, you can play him in ANY GW deck turn 1 and get 2 extra willpower. And then he can chip in with his attack, which can be boosted with For Gondor! and its ilk. With Visionary Leadership and Faramir, he can quest for 4 without exhausting! I don't know why he isn't a staple yet. Only 96 decks on RingsDB have him. Highly underrated card.
I love this card, not just because Dwarf decks are my favourite, or for the memory of Thorin's last, valiant charge. For 1 resource (and only 1 Dwarf hero, so it's not limited to Dwarf-only decks!), you can put any discarded Dwarf ally first into play and then back into your deck. This can be useful for many situations: pop in a Longbeard Elder if you need a bit more , or a Veteran of Nanduhirion or Veteran Axehand if you need some extra . If you need temporary then there's Longbeard Sentry or Erebor Guard. Alternatively, if you didn't want to pay the extra upkeep cost for Dwarven Sellsword, then you could bring him back for a phase with this, as well. Or maybe a dwarf ally you like just happened to die too soon. Dwarves can fill nearly any role needed, so being able to call one on command is rarely a bad thing.
I am sure that there are several combos that one could devise to get more benefit out of the ally being returned (for example, delving Soldier of Erebor or poor Brok Ironfist, then using To Me! O My Kinsfolk! to pair with a use of A Very Good Tale). It is also good, for allies you'll want to actually play again, to use in a deck with the in-trait Bofur, who can shuffle your deck for you to bring your summoned ally closer to the top of your deck.
But what I really wish to suggest--in combination with the Bofur shuffle above--is to use To Me! with those Dwarf allies with enter play effects. Most Dwarf allies with their effects have the "When you play from your hand" qualifier, but a few don't: Miner of the Iron Hills, Longbeard Orc Slayer, and Ered Nimrais Prospector all trigger effects upon entering play with no other qualifiers. That means that To Me! becomes a 1-cost recursion for Condition removal, damage to all Orcs in play (especially useful in scenarios like Into the Pit and The Seventh Level), or recurring other cards back into your deck. The added benefit is that these allies are, as mentioned, put back into your deck, allowing you to make use of their abilities at least one more time. This event is very versatile, and by extension makes your whole deck just a bit more versatile as well.
I agree with Warden of Arnor's review. One small change that I think would make the Guard more useful if he had the Warrior trait, especially with the expanded card pool we have now. Without any changes, he can take Ancestral Armor, but that's too expensive to waste on the Guard unless you're desperate. But with the Warrior trait, he could take the far cheaper (and still in-sphere) Hauberk of Mail, which would put him at 3 & 2 with the potential to ready him to take multiple attacks. That seems much more reasonable to me.
Without that change, you can also now give him the (also in-sphere) Squire's Helm. 2 and 4 isn't the most awful, especially with Doomed cards that often want to be played during combat, like The Wizards's Voice and Defiant Challenge (which you could use to ready Orthanc Guard to defend and attack and another character to attack the enemy in turn). In my Doomed deck, I personally like to use him to quest then ready him for defending like I just described, to get just a little bit more out of his stats. Is he the greatest ally ever? Not by a long shot. But with the newer cards and additional support for Doomed to make it a more viable deck, I also don't think he's the worst ally ever. Just probably not really one you'd want to run outside of a dedicated Doom deck.