So, is Mobility ONLY a special class ability or can it be taken as a feat by anyone?
Which makes it a bit annoying for Soldiers -- as they can't get Whirlwind Attack without multiclassing five levels into another class, yet it's specifically listed as being a feat they can take with thier bonus feats.

Really, this seems to be another case of the different rules between D&D and Conan not being fully accounted for -- this time in the listing of Whirlwind Attack in the FAQ. Soliders can still get it, but not as Soliders. Not really a mistake, but mildly annoying none-the-less.
Aw, c'mon guys. Just because it's not listed in the book doesn't mean you can't use it. It's not like it's a magical feat that doesn't fit the Conan setting. If you don't have a PHB from DND, then just go here...

Or better yet...

Prerequisites: Dex 13, Dodge.
Benefit: You get a +4 dodge bonus to Defense Value against attacks of opportunity caused when you move out of or within a threatened area. A condition that makes you lose your Dexterity bonus to Defense Value (if any) also makes you lose dodge bonuses.
Dodge bonuses stack with each other, unlike most types of bonuses.
Special: A soldier may select Mobility as one of his soldier bonus feats.

Look, I even changed 'fighter' to 'soldier' and 'Armor Class' to 'Defense Value'.

That's the coolest thing about Conan RPG, DND and other d20/OGL systems is that you can change them as you wish. You can mix and match if you want. You can even make up your own stuff. It's not like ANY of the books are THE rules... They're more guidlines to spark our imaginations and so that we don't all have to come up with our own books to be able to play.

Sure, maybe it was an oversight for Mongoose to either leave out Mobility or forget to remove it from the prereqs for Whirlwind Attack. No need to tear them down on every little error. We're big boys, we can handle it.