That being said, would it be worth lowering the set difficulty in the miner to 512 (the next lowest setting) and setting min diff in the worker setting on bitminter to the same?
If you think 1024 is giving you too much daily variance then you can do this. I think 1024 should be fine though.
I have found that if you set the diff in the miner to anything equal to or lower than the diff size sent from pool they run fine. If diff from pool is smaller than work size set in miner config, they run very slow. I set mine to 128 in the miner and this way even if pool starts off at diff 1 it can do them fast enough to get past 128 and will eventually hit 1024. Best is just set worker for pool to 1024 and 128 or 256 on miner end. I go with lower (128) since backup pool cant set the min diff.