I'd actually say that Doric and Scots are either

1) Dialects of English

or

2) Pidgin languages derived from English, Gaelic, Norse languages, etc.

The definition I'd always been given was that dialects are mutually intelligible (i.e. an American can go to Scotland and understand what Scots are saying)... I think it's pretty convincingly a seperate language with Doric... I know there are Doric words I wouldn't get at all if I hadn't been told what they mean.