It's not a matter of there being a problem with the springs, its just that a 2 - 2.5" drop is pretty much gonna max out the adjustment range on any of the cams. I've heard of some people going with a 3" spring and getting the alignment real close, but every truck is a litle different. Also, you really need someone who's willing to take the time to align our trucks properly, its not the easiest, nor cheapest thing to do correctly.
On another note, while using a spring is a quick and fairly cheap way of getting 2" of drop, I would NOT recommend it as the first step on a 2wd truck. The loss of suspension travel, difficulty with alignment, and stiffer spring rate will make your ride pretty bad. I speak from experience on my 94 Ranger with Steeda springs and my 93 Ex with Eibach springs. Go with drop beams, you'll be much happier with your truck. Unfortunately, on a 4wd, springs are your only option, so if you really want it lowered you're going to have to deal with this stuff.
-Dan