Elladan, along with his brother Elrohir, is somewhat despised by most players because for one to work, you need the other in the same deck; severely limiting the options. One of their best uses is in a fellowship with the twins in different decks, but that brings up the problem that they're not Ranged and Sentinel. I do think the brothers can be very powerful if you can work them in, especially once you build up their resource pools a bit. One thing of note is that with the new ally versions in MoF, there are now new interesting combinations for the elven twins.
Elladan
Noldor. Noble. Ranger.
While Elrohir is in play, Elladan gets +2 .
Response: After Elladan is declared as an attacker, pay 1 resource from his resource pool to ready him.
The Return of the King
Road to Rivendell #28Tactics.
Making Elladan and Elrohir a thing is quite difficult I find. Forth, The Three Hunters! at least helps with one of their biggest problems (needing resource-intensive attachments while having resource-based abilities), however they usually still need said attachments to get going, in the case of Elladan mostly Rivendell Bow to give him ranged (since running a dedicated tactics attacker in solo is not something I would recommend as a general rule) and then some other weapons like War Axe or Rivendell Blade to boost his attack strength. This not only takes time, the payoff here is also only average.
The biggest saving grace for Elladan, and the reason why most of my twin decks are not just using Messenger of the King for his otherwise more useful ally version, comes in the form of Orcrist. While this combination still needs a little time to be set up and get going (needing to defeat a guarded card first is certainly a huge downside), the ensuing payoff is pretty great, with Elladan suddenly reaching his ultimate machine-gun form. The setup is bothersome as discussed and probably only makes real sense in higher player counts where there are sufficient enemies to be worth it, however it does save Elladan from being a total disappointment for me.
Rating: 4/10