I hearby declare Avian Tactician and Undead Merchants/Warrior/Tactician to be the best overall race combo ever to exist for attackers.
If you are looking for your kd on which races to play for attackers, choose those two. Avian tacticians because you'll be so fat because of all your super fast attacks (plus you can fly, *joke*). Can you imagine attacking close to 4 times a day in war? HOLY CRAP. Plus the added defensive bonus makes Avian Tactician THE ultimate race to play. Game over for that war.
Undead/Merchants because of the extreme power of it. You'll need a few high off provs to take down the MANY turtling faeries that will pop up next age. Merchants will be necessary to afford the elites.
Don't bother with humans, the sci bonuses aren't that great. Dwarfs are weak, the BE bonus won't make that much of a difference when your pop is kept low from all the avian attacks on you. Orcs are only ok, undeads outshine them in every way.
There you have it. Top kds don't want to share this info with you becaues they are afraid everyone will steal their strategy. Well I just shared it, you're welcome.
Ok, commence the many naysayers trying to discourage you from using this strat so everyone doesn't clone their kd. Just don't listen to them.