How to stop burning raisins in my fruit scones
Since raisins are a type of dried fruit, they don't have a lot of moisture left in them. Heat from baking with just make them drier, eventually resulting in that chewy, not particularly pleasant lump. The internal raisins are more protected from the heat, so they stay the same consistency.

One solution may be to soak the raisins in water, fruit juice, or even wine (boozy scones!) before cooking. The extra liquid will help prevent that drying effect; you'll still have some consistency difference between "outside" and "inside" raisins, but none will be inedible. I soak raisins as well as dried cranberries and cherries before using them in muffins.