Don't let the "0" cost lead you into thinking this card is a "must include".
I'm not a big fan of the Dunedain Pathfinder ally if you mostly consider its near and mid term effect on board state when deciding to play it. Sure the 0 "resource" cost is tempting, but there are other hidden costs....
Just looking at the 53 eligible location cards in the Harad cycle AP packs it comes from, 9 locations have 1 , 23 locations have 2 , and 21 have 3+ . This is counting multiple copies of each eligible location in the encounter decks.
That means roughly 40% of the time you are going to increase the staging area threat by more than the 2 you get from this ally, and another 40% of the time you are breaking even. Short term this is not good.
Now in exchange you get a zero resource cost emergency chump blocker and some long term upside of having 2 more per round for no resources spent - if you can keep the ally alive. However, this is not a "net" +2 as you still have to overcome the additional of the added location card that came with deployment of the Pathfinder before you get a "net" bonus.
And if this poor net / exchange wasn't enough to give you pause, there is also the chance the Pathfinder finds no eligible location, and goes away without deploying. This is equal to one turn of card draw with absolutely no return for it, when you could have drawn something else more predictably useful.
Now let's compare this to Celebrían's Stone, which gives you net +2 on the turn you use it, and every turn thereafter. You are also less likely to lose the hero it is attached to as you would an ally. Yes, this counterexample costs 2 resources, but very few cards are truly "free". ( Unlikely Friendship being an example of one that is almost truly free.)
This card has its uses - quick deployment of a chump blocker for no cost, when quest threat isn't an issue. It is a better card when the encounter deck is mostly <2 locations.
However, the hidden costs of this "free" ally may not be worth it in many situations.