Just wanted to chime in by agreeing with the idea of practicing things very slowly (which Tony and others have also emphasized). I've spent a fair amount of time practicing drum set grooves as well as hand technique exercises super slowly (for example, with the quarter note on the metronome being set anywhere from 40 to 60 bpm), and it's been very helpful in improving my precision/accuracy and overall timekeeping. Try practicing the single beat exercises from Stick Control at quarter note=60 for 15-30 minutes per day. Or practice some drum set grooves at 40-60 for 30 minutes. Resist the urge to bump up the metronome speed once it feels like you are getting a handle on the patterns--continue to sit at the slow tempo for a while longer (over the course of a practice session, or a period of days, or even weeks), and I think you'll find that your timekeeping and consistency will improve quite a bit. Just remember to stay focused while playing at the slow tempo, and really concentrate on the quality and consistency of your sound.Many ideas and concepts to toss out there but start by playing whole notes at 35 BPM - no faster.
Then the table of time at 35 BPM - no faster.
Then everything you're currently shedding at 35 BPM - no faster.
Then up the click to 40 BPM and repeat.