Mostly, it's offset by the fact that you get to use a longbow or any other ranged martial weapon. The -4 int is partially a flavor thing... it represents not having gone to school. I might be persuaded to add a plus one or two to wisdom though, to make up for that. Wisdom doesn't come from books, after all.
Specifically for THIS campaign, Explorer has even more benefits because you get Wilderness Lore as a class skill. I believe that will come in handy... very much so, in fact.
By the way, I'm also going to add a campaign specific feat that I think will work well. Useable by any class as long as you meet the requirements.
Friend of Navan
You are welcome in the Navan forest, and even able to leave it.
Prerequisite: Must either posess Epic Levels in any class, or possess inherant innocence... including a child-like wonder at everything seen, no desire to create detailed maps, a playful heart, and a willingness to be led where the pathways lead wherever they may go.
Benefit: The forest opens up its heart to you, and will allow you to leave when you wish. Various other unspecified benefits that only take place within the forest.
Normal: The Navan Forest is a dangerous, DANGEROUS place and few who enter ever return.