The dual ab thing you noticed Tyr happens with other chars as well. Its the haste that ignores the dual penalty, and does so for all dual wielders. No idea how it looks on a barb using the large dual weapons and that could be interesting.
Regarding the AB bonus against FE, that sounds interesting but should not break the +20 cap (any idea if it did). So with +13gmw, +6song, it should only give +1 anyway.
Another consideration, keep an eye on the behaviour of Craft Weapon ab bonus while dual wielding, I doubt its doing anything but if you really seeing some quirks you never know.
Anyway the known one is that haste ignores any dual wielding penalties (and possibly other penalties as well but would be surprised if it did) as its attack is always at maximum. The haste can be seen after the main hand but before off-hand I believe.
I must say my ranger is pretty close to this one so if there is anything strange about AB its only minor: My char is Ranger/WM as well with AB as follows:
30 BAB 22 For 54 Str 7 for WF/EWF/EP/LWF 1 for WM 20 for +13 GMW, Bardsong, Aid, FE. 15 for full LBAB ---- 95
So dual wielding it drops to 93, however the haste attack will be 95, and when flanking that haste attack will hit 97.
So we can see my AB is very similar to this builds, and will be close if they also taken Craft Weapon. However I would stress I would never have my Str that low for anything but a full 1/1 tier class combined with WM and also craft weapon. It also does rely upon bardsong or other buffs quite a lot.