It is noteworthy that both of them are evil viziers who usurp the throne and take over the kingdom, and both of their initials are "A.A. Was this intentional?

Completely coincidental.

Abdul Alhazred was borrowed from Lovecraft.

Ad Avis was named after Bill Davis of Sierra at the time. The Coles did this a lot in the QFG series; Rasier is an anagram of Sierra itself.