Someone mentioned not compressing because the samples are already compressed. This may be true for some sample libraries, but for some, like DFHS, they are totally dry samples. No effects of any kind. Compression and EQ are an absolute necessity.
By the way, to the original poster, DFHS is a great program for doing programmed drums. Most people swear by it.
When I program, I try to think like a drummer. I'm not a great drummer but I can play enough to help me do that. It helps alot to be able to visualize what you're programming as being physically played. If I can't do that I won't program it that way.
Another thing is the velocity range you use. First of all, 127 should represtent the absolute hardest hit you can muster, and in DFHS that is what it sounds like. How often does a real drummer hit anything as hard as possible? We all like drummers that hit hard, but programming drums that sound like that perfect, hard hitting drummer are the surest way to sound fake. I've found alot more realism in DFHS by keeping the velocities at around 100 or even lower for most hits. The odd accented hit might creep up over 115 and using 127 would mean I was trying to kill the drum. At least that's the way I think of it. Doing it that way, when you process the tracks as you would a real drum kit, you get much more realistic results.
Remember that when doing rolls and fills, most drummers don't hit the snare or toms that hard, and they don't maintain consistent power. Long fills will usually fall off in velocity with a few "spikes" to keep the feel together.
I might add that when doing extreme metal stuff I go ahead and use the max velocity accross the board for the kick drums. The triggered sound is so much the norm these days that anything else would actually almost need a sample added to it in order to compete.
When it comes to processing of the drum tracks, the same principles apply as when working with real drum recordings. You should search the internet for tips on EQ and compression for drums - not just programmed / sampled drums.