A sorely under-rated hero. Granted, he's not quite Beregond (or even Beregond), but 3 is still solid enough to withstand the majority of enemies, barring shadow effects. Speaking of which, innate shadow cancellation is an incredibly valuable ability for a defender to have. Potentially worthy of note is that there is no limitation on his ability, so it can work even if the attacking enemy has multiple shadow cards you want to cancel - the only limit is of course Erkenbrand's hit point total.
Using Erkenbrand against higher enemies is admittedly a more risky prospect, since combining damage from his ability with damage from the attack can easily put him at risk of death, but with any dedicated defender you should be considering -boosting cards and in general you should always consider bringing healing, but especially with a hero like Erkenbrand who triggers his ability by taking damage. Dúnedain Remedy is the in-sphere option, beyond that you want to be looking at the sphere (I should point out that while it still helps with defending, damage cancellation effects are of no use for Erkenbrand's shadow cancellation - if the damage is cancelled, the shadow effect is not). Warden of Healing is obviously the standard, but since we're focusing on a single hero Self Preservation and Lembas are also excellent choices for Erkenbrand, and basically anything works.
There are a couple of ways to further improve Erkenbrand's ability to disregard shadow effects - with readying so he can defend more attacks obviously, and by increasing his hit points so he can trigger his ability more times before needing to be healed (particularly relevant if your healing is Lembas and you want to get the most out of it). Armored Destrier is a great option since it readies him and discards another shadow card, making that enemy safe to be defended by someone else, but another valid option is Raiment of War - if he has other readying (like the standard Unexpected Courage) then the boost may not go to waste, the boost obviously helps, and 2 extra hit points help with his ability as noted. For a non-Restricted possibility, Ent Draught also adds 2 extra hit points.
It can certainly be argued that Erkenbrand is not the ideal defensive hero. He lacks a Gondor trait to synergise with the Gondorian Shield or Blood of Númenor, and shadow cancellation can be provided through other means, including the ultimate option in A Burning Brand, though this may require a Song of Wisdom to get it on a lot of the better targets - but that really highlights the worth of Erkenbrand. While Beregond has higher base , getting him repeatable shadow cancellation requires a two card combo. Innate heroes have immediate access to Burning Brand, but that's still dependent on drawing it, it costs 2 resources, and they all either have lower than Erkenbrand or lack his Sentinel keyword - Erkenbrand is the only 3 hero with Sentinel we have in the game thus far. So other defenders may have a higher potential, but Erkenbrand starts stronger and can save the game early on, before you draw all those important boosts you need Erkenbrand's closest competition for early game shadow cancellation is Balin, but aside from not being such a great defender himself and thus most likely consuming an additional hero slot in any hypothetical deck, Balin requires resources for his cancellation which you may not have available, especially in the early game; whereas Erkenbrand's hit points are guaranteeably going to be ready for use whenever you need them (unless he's already taken too much damage).
Overall, if you're not concerned about shadows then sure, Beregond is better, and cases could be made for other heroes, though Erkenbrand still definitely holds his own; but if shadow effects are a significant concern for you, then Erkenbrand's front-loaded innate cancellation combined with his stats and Sentinel is about the best you're going to get - having cancellation based on damage and having to wait to draw/play healing may be preferable than having to wait to draw/play your cancellation and being killed by an early shadow effect before you have it. How much you're worried about that depends on your approach to the game and perhaps what quest you're playing, but if you expect it to be a problem then the Lord of the Westfold might just be able to save the game for you.