Other than the easier transmog, the perks of being a human are every man for himself, diplomacy, human spirit, mace and sword specialization. Human spirit is 3% spirit, which is useless to us mages. Every man for himself is useful in pvp situations, and also some raiding mechanics to remove impairing effects.. Diplomacy is probably the most temping racial because of the increased reputation gain. Mace and sword Specialization grant 3% to expertise (hit for spell casters).
When it comes to playing a mage, the specializations are useful but unless you get a sword and plan on keeping swords the entire time it may not be worth it.
The diplomacy is nice for rep grind, and every man for himself is good to use in pvp and arena situations.
The space goats, or at least is what I've called them since the release in BC, have a few interesting racials. Gemcutting, the gift of naaru, heroic presence and shadow resistance. Gem cutting grants 10 extra points in jc. This racial is good for leveling and maintaining jc but not beneficial to leveling or playing a specific class like a mage. Gift of the Naaru is a very helpful survivability ability. It grants 20% healing over 15 secs. Heroic presence is 1% hit to casters and melee hits. Shadow resistance is what it says with the bonus shadow resistance.
When it comes to playing a mage, the gemcutting bonus is nice only if you are a jc. The gift of Naaru is great in pvp and pve situations, anywhere where you take damage really. The heroic presence is the key to happiness as a Draenei.. This means more reforges into other beneficial stats after you reach hit cap. And the shadow resistance is nice but not really worth aiming for.
There are a few racials here: explorer, crack shot, mace specialization, frost resistance, and stoneform. Explorer is an archeology ability, allowing dwarves to find more fragments at each dig and also helps with finding spots faster than regular archeologists. Frost resistance is what it's is, more resistances to frost. Crackshot adds 1% expertise to ranged weapons. Mace specialization adds 3% expertise for 1h and 2h maces. Stoneform removes all damaging dots and reduces damage taken by 10% for 8 seconds.
For mages, crackshot and mace specialization does not apply. The archeology buff helps if you are into archeology, but doesn't give anything special when it comes to raiding. Stoneform is a pretty sweet ability. It is taken from heritage of the dwarfs and their ancestors, the stone dwarfs. This ability is useful in pvp situations and some damage taking portions of raids.
Here are the gnome racials: arcane resistances, short weapon specialization, engineering specialization, escape artist and expansive mind. Arcane resistance is what it is. Resistances to harmful arcane spells. Short weapon specialization is 3% expertise to daggers and 1h swords. Engineering specialization adds 15 to engineering. Escape artist allows user to escape from any immobilizing or slowing effects. Expansive mind increases the mana pool by 15%.
For mages, the expansive mind is the only thing that is beneficial raiding wise that gnomes have to offer, and it is pretty much one of the best racials out there. Which mage wouldn't want more a
Bigger mana pool? The engineering specialization is good for engineers out there. The short sword specialization is good for casters if they plan on keeping swords or daggers as their main hand weapon. The 3% expertise translates to hit and its very helpful for reforging into helpful stats. Escape artist is good for survivability in pvp, and a few spots in pve but pvp mainly.
Night elf racials are as the following: shadow meld, wisp spirit, quickness, nature resistances. Shadow meld is fun. This is like a rogues stealth but available to all nightelfs. Wisp spirit changes your ghost form into a wisp and you also have a 25% increase in run speed. Nature resistance is what it is, resistances to all nature spells. Quickness is a chance that all attacks (range or melee) have a 2% chance to miss against you.
For mages, the only one useful is the quickness ability when it comes to pvp. The shadow meld is also fun, but can really be beneficial in the pvp aspect of the game.. Wisp spirit is fun but no real benefit in pvp or pve.
The racials for worgen are as the following: aberration, darkflight, enable human/worgen form, flayer, running wild, two forms, and viciousness. Aberration is the increase of shadow and nature resistances. Darkflight, when activated, increases run speed by 40% for 10 seconds. Enable alter form, allows user to swap between worgen and human form. Flayer increases skinning skill by 15 and increases skinning speed. Running wild drops user down to all fours and runs like a wolf. Two forms correlates with enable alternate forms. This ability allows you to switch between wolf and human. Viciousness increases critical strike by 1%.
For mages, the only ability here worth noting is viciousness. The 1% crit is very powerful. Fire mages would enjoy this very very much. Frost mages enjoy this as well with their quest to get 23% crit for critical icelances. The other abilities such as aberration and darkflight are survivability abilities, especially in pvp. The alternating of forms is fun but useless in my opinion. Flayer is good for skinners and running wild is just for looks.
All in all the two best pve races for mages in my opinion are gnomes and worgens. You cannot argue with the mana pool increase or the critical strike. Dwarf and nightelfs are very powerful pvpers and humans are good for rep grinds and transmog.