If we are talking about a stealth class, archery, or melee, sure I'd agree. But when it comes to a magic based character, the altmer racial is a clear cut benefit above all other races. Considering magic is just SO gimp in Skyrim, especially at higher levels, having to empty your ENTIRE mana pool to kill a single enemy, and 3 times over for a boss/priest/deathlord, highborn is invaluable.
The extra 50 magicka from an Altmer is nice but not needed.
Heck the arch mage is a Dunmer,theres no magicka bonus there.
Any race can become a good mage.
I think an Orc necromancer/mage is a good idea.