You don't understand. That was all we had. Mages have more tricks to get away from people/mobs, the only other thing Warlocks had for kiting was Curse of Exhaustion (which isn't that great, plus we have no other speed buff to maximize its use, like a Hunter has Conc Shot/Wing Clip + Cheetah).

Curse of Exhaustion you had to dump 25 or so Talents in the Affliction tree to get it, and it still only slowed to 70%. It's just not good enough.

Warlocks operate mainly upon Attrition, with their DoT's (hell, if you're using Curse of Exhaustion, you have to sacrifice using one of your major DoTs to even use Curse of Exhaustion). That means we don't deal large amounts of damage in bursts, it accrues slowly over time.

Having 'Fear' buy you maybe 8 seconds (2 DoT applications), you might have done 100 damage with DoT's (Level 35 skills), and maybe another 300 with Shadow Bolts before you're in our face hammering our poor, Cloth-ridden asses into the dirt.