D&DXP: Skills...

[jeffh]

The Ranger's +2 to History is a Racial modifier for being Eladrin; therefore, I suspect the Warlock's +2 to Insight might be for being Half-Elf.

Halflings and Acrobatics too, I'll bet, which resolves the discrepancy the OP attributed to inconsistent armour penalties.

 

[Fifth Element]

Nature - Wis or Int. Ranger seems to use Wis, while the Wizard seems to use Int.

Or Int is the key ability for Nature the ranger gets a +1 bonus to Nature from his class. Seems more likely than having a single skill that uses the better of two abilities?