These kinds of samples can be just put a 16th or 32nd or whichever works before the beat - it's quick to do and doesn't lock up, say, the entire snare track.
That method might work better in DB if, say, one could expand the grid for a single measure selectively, without making the entire "score" so detailed that it becomes hard to read more than a brief span at a time. Maybe a compromise solution, in which just a few well-chosen positive or negative "percentages" were available as options for making attacks start a little behind or ahead of the beat, might be possible. Strokes so altered could perhaps be shown on the screen in a special color or shading. But what about rolls and other strokes that you sometimes want to persist after they are hit, and sometimes not? -Sterling