My favorite cards in the game are those utility cards who's value is not immediately obvious. Mirkwood Pioneer definitely qualifies as one of these. I can remember when this card was first spoiled, and the almost unilateral response of the community was that he is underwhelming. I shared that sentiment also, until I started playing him in decks.
The first time I played Mirkwood Pioneer was purely serendipitous. I was playing one of my favorite scenarios, "Riddles in the Dark", and was trying to stack up on 2 cost lore allies to beat the riddle mechanic. The first time I played this guy, he blocked staging threat from an enemy, allowing me just enough progress to clear the active location... and then he chump blocked that enemy allowing me to engage and destroy it. That was the first time I realized there was more to this card than meets the eye.
Firstly, 2 cost allies are always good because they fall in the chump blocking range. Even though Mirkwood Pioneer is a bit pricey for his stats (allies typically double their cost in stat points) he has the stats where they count. Defense is meaningless for a chump blocker, and very rarely do I tend to use "weak" allies in attacks. His 1 willpower allows him to quest, and his extra hit point even allows him to eat some archery damage while he is waiting to do his sacrificial duty.
Of course the true value of the Mirkwood Pioneer is his chump blocking combined with his ability, which is staging threat negation akin to Radagast's Cunning, Secret Paths, or Fatty Bolger. Staging threat negation may not seem like a big deal... until you are a few progress short of clearing an active location resulting in location lock, or fall short of completing the final quest card just before threating out. The truth is, this ability is extremely useful in clutch moments, and marginally useful for questing all of the time. Unlike Radagast's Cunning or Secret Paths, the Mirkwood Pioneer can target both enemies AND Locations (and even treacheries!), and his targeting flexibility is why I prefer him to these cards. Doomed 1 is an additional cost, but a fairly marginal one in my experience...especially in solo play.
The Mirkwood Pioneer truly shines in my mono-lore Ranger/Trap deck, where he pulls double duty. He both helps to manage the staging threat of enemies that I'm "fixing" into the staging area, as well as standing available to chump block the odd enemy that slips through my traps. You definitely want to think twice before you put this one in the bike spokes, as Mirkwood Pioneer has saved my bacon more than once.