I also use the concealment on favored terrain for my alt. ranger, and I like the way you've handled yours. Although I don't like the concealment AND the AC bonus, in my opinion it should be one or the other. Why? Because in the heat of combat, having a player remember their ranger favored enemy bonus is hard enough, then remembering the AC and the terrain is just a lot of math and extra work that I as a dm and a player don't want to deal with.
I suggest upping the concealment by 5% (since the + to AC is about equal to that).
Also, I don't like wilderness master. If you want to go that route, why not just add another favored terrain and go that route? These bonuses for the ranger are very good, and so should have some limitations. The ranger should be the man on his home turfs, but allowing him advantages virtually everywhere is unbalancing in my opinion.
Finally, I've had the idea of combining several of the virtually worthless favored enemies into one category. Like combining plants and oozes. Why? Well from an RP perspective, a ranger doesn't have near the work to do to learn about plants then he does against orcs since bluff, extra damage, sense motive all don't work against them. Same with oozes. I believe it makes sense for a ranger studying both oozes and plants to be able to do it in the same amount of time as a ranger studying ALL the aspects of orcs. And it makes those choices at least a little more viable.