Warlord
Warlord is an interesting hero, and one that often commands a very high cost.
He is a giant of red type, so unless you are an Eradication with Fire Giants, he will never lead a stack and give it an efficiency bonus. He gets no abilities at all until lvl 14, and has a tremendous gold cost. At 12th lvl he would cost 70,000 geld a turn and provide just a meager melee attack! So unless you got geld to burn, I wouldn't recommend getting him until at least 13th lvl.
His Tactics ability is what he is purchased for. Tactics raises accuracy by 1% a level. Considering all regular attacks (and defense) starts out at 30% accuracy, a 1% increase is a bonus of 3.33% to your overall attack.
(Please correct any math mistakes.)
While a Valor hero at lvl 14 would provide 9% to primary (only) and counter AP, this is still reduced by accuracy, efficiency, random number generator.
So if you take a 100,000 primary attack modified by a lvl 14 Valor hero, that gives you 109,000 base AP. Modify it by .3 accuracy = 32,700. Assume a .5 random number generator = 16350.
Take the same 100,000 primary modified by a lvl 14 Warlord and you modify it by .333 accuracy = 33300. Assume a .5 random number generator = 16650. Or a bonus of about 1.8% over Valor. But it works for Primary/Secondary/Counter and not just Primary/Counter.
MOREOVER, during sieges, your base accuracy is 20%, not 30% (if the units can't fly or have Siege ability. In the same scenario, Tactics is better by about 6.89% because the small bump in accuracy is a much bigger % of your starting point. At high Tactics levels, this difference increases more.
