Sauron vs Voldemort

[Ditto]

If orcs hide by day, wizards hide by night. Easy enough. And wizards are safer when camping, too!

For specific issues, wizards can bweem daylight. Summoning flame shields (yes, there's always Fiendfyre, but wizards make *normal* fire too, a la Dumbledore in HP6) is functional *and* pretty. I'm sure they could rig up some sort of darkvision spell, but human transfiguration isn't taught til 6th or 7th year so a little Lumos is just a cleaner way for everyday use. If Sauron blots out the sun, that's an issue for targetting to be sure, but the best kinds of spells against an army are AoE, right? You don't have to be too precise.

I don't recall ever putting too fine a point on finding the targets, let's see... I believe there's a 'Prying Eyes' analogue... I can't put my finger on it, but I want to say it was used notably in the 5th book. I believe Patronuses could serve the purpose of scouts (if this team weren't all evil). Flying around on a broomstick under an Invisibility Cloak or disillusionment charm would be good, too. Hominem Revelio might be adaptable into a narrow cone instead of a radius burst. And the orc army is generally easier to find than a few dozen wizards are due to the size of the force alone. I don't think it's one of the main issue here, really.

Corrupting is another tack, I suppose, but it ultimately comes down to who has the most souls to steal, and that's unquestionably the thousands-strong Sauron team. It's not about who's more evil among evils; when forced to choose the good guys or the evil guys, they'll go with the evil guys because they're a bit looser with their prisoners, nothing more.

EDIT: Dementors are the manifestations of fear. Nazgul are men. Nazgul are men with a supernatural ability. "Soldiers aren't happy"? Well, duh. You need to talk to some soldiers, friend... not enjoying foxholes is different from the sudden certainty that life is not worth living. You're also pretty flip with the 'rip out your soul thing'... when you get stabbed, you can get better.