UniversalWolf: From my experience the ranged attacks from common DE units like Swordsmen, Cavalry, and Nightmares start out very weak, but increase dramatically in effectiveness as the experience level of the unit rises. The ranged attacks from, say, a group of Champion level Dark Elf Cavalry are quite potent for a unit with very good melee combat ability (especially with Adamantium). The Nightmares are even better. When they're inexperienced it helps to wait until the enemy units get fairly close, like less than 4 squares away.
Priests and Warlocks, like most spellcaster units, can snipe from far away still do damage.
You may be under a misapprehension. MAGICAL RANGED attacks do NOT suffer ranged penalty so it does no good/bad to wait for them to be within 4 squares.
Dark Elf Spearmen are the best to use early for Ranged Attack Strength. This is because they have 8 figures and all the Ranged Attacks start at 1 and increase by exp level the same amount, (minus Priest, Warlocks and Nightmares). They start at 1 at Recruit, 2 at Regular and Veteran, 3 at Elite & Ultra Elite and 4 if you can get them to Champion. Therefore Swordsmen and Halberdiers are not that useful, in fact I never build them. Even Cavalry suffer a bit because they HAVE to use those magical ranged attacks before they can use their melee attack. I would rather build Night Blades if I need fighters as they benefit from Adamantium greatly.
I love to have Flying WarLocks (usually through Chaos Channels). So nice to take out Great Wyrms with them hehe.