chorolus, we're not having a flame war. If we -were- having a flame war, you'd see mods here any moment.

We're having a spirited argument. I'd prefer if you showed better courtesy and clarity -- and yes, how you act is going to influence how you're treated -- but that's another matter.
Part of the problem is that you're not really making clear -where- your disagreement is.
There's no argument (or room for same) on how SFA works (nor on how the Sharpshooter -- which gets this ability with a bow or crossbow at 11th level, works). -if- you can make an OA, you can make it as a ranged weapon. So all those OAs you are denied because they're too far away (like the one provoked by Beast Protector) can be made at range -- and normal OAs made at melee can still be made at range.
So unless you think that SFA lets you make an OA on any creature in your penumbra that walks or makes a ranged attack (in which case, you should talk to customer service and present them with your very original interpretation), the disagreement is on how Reaving Axe Slayer works.
As it turns out, the game does not (as I mentioned upthread) have a game definition of "threat range" or any such -- or at least that's not in the compendium. It probably should, but they've tried to port over that concept without adding new terminology. So the fact that Reaving Axe Slayer doesn't say what the target provokes an OA from is really a bug in RAS -- there's a legitimate disagreeement (if you've agreed with me up to here) in whether one views RAS as saying "provokes an opportunity attack from all enemies" or "provokes an OA from adjacent enemies."
OTOH, look on today's article on rules updates for a little hint of how Wizards tends to think about these things:
GB: Those are the easiest errors to fix. I remember when Divine Power came out, people looked at solar wrath and wondered how long the effect lasted. Although we (R&D) might take for granted that an encounter power’s effect almost always lasts until the end of the user’s next turn, many players have no way of knowing that, so until we issue an update, people have to guess at how long it lasts.
Ok, so lets look at RAS here. It doesn't specify who the target provokes OAs from. "everyone" is clearly -not- the right answer here; it's totally out of scope with similar powers, nor is there a general rule that even vagule implies it. So the two reasonable answers (and while I favor one, I could really see arguments for either) are:
1. They provoke OAs from -you-. Look at the Thug Specialist for an example here. In this case, your buddies standing next to the guy you knocked down wouldn't get an OA from them trying to get up. But you would. This is a reasonable ruling if you think they just left some words off the feat.
2. They provoke OAs from adjacent enemies. Look at how OAs work in general -- nearly all OAs are provoked from adjacent enemies -- Beast Protector and "from you" are pretty much the only example otherwise. This is a reasonable thing if (like me) you think they'd assumed there was a general rule that you could only react to OAs provoked by adjacent enemies, and so didn't think it needed to be said.
Basically, as written, RAS is a do-nothing feat (they provoke OAs from who? Well, nobody, since it doesn't say) that requires a table ruling. If you can talk your GM into letting you use ruling #1, then your build works fine (more or less), and isn't significantly overpowered. If your GM instead wants to go with #2, that part of the build doesn't work. And if you're trying to go with "all enemies", your GM -should- slap you down for that, because it's clearly an overpowered misreading of the RAS feat.