I know that sample tweaking and having multiple samples of the same instrument can sound daunting, to say the least, but usually, some drumkits in some modules or samplesets already have velocity layers built in. This means that the sample changes as you strike harder or softer. So, in order for a drum track to sound less static, vary the velocity over the length of the loop. Make the loop long, something like 8 or 16, even 32 bars, making sure the velocity changes for every hit along the length of the loop.
Listen to most drum tracks. The further you go into the song, usually more elements are added into a kit. The drums usually start out simple and get progressively more complicated. It's an "ebb/flow" thing when it comes to complicating and "de-complicating" a drum track. Also remember that fills are part of the transition from verse to chorus.
Other secrets? Ghost notes, flamming, silent sections (aka "breaks"), and my favorite, strategically placed "mistakes" - makes a drum track come alive.
Common processing mistakes? Assigning all elements to the same reverb. Usually the kick isn't reverbed and if ever, you eq out the lows so that the low frequencies don't overwhelm the mix. I usually try to simulate a 4 mike setup by having a kick track, snare track, then everything else goes into the 'overheads'. There are other, more esoteric processes to make a drum track clear and cohesive. This can be discussed at a later time.
hth,