Alright, I've calmed down from that last death to continue on. I've automated dirt generation, but my current mob grinder is not adequare enough: A dark room with a cobblestone floor and a grinder in the middle. Time, I'd say, to upgrade. How? simple. By replacing the cobblestone floor with one made out of cursed earth.
The grinder works a 5x5 zone in front of it. Putting it in the middle of the room means at least half the room is behind it and isn't covered. Put it in the wall for better coverage.
Also, mobs will only spawn if you are at least 24 blocks away. Make sure you build the room a ways away from your base so you aren't getting too close and stopping spawning.