bitminter is a low fee merged mine PPLNS pool, on paper looks good, but somehow, their 'luck' is extremely rotten - just check the income section and look at CDF. Check the luck and reward section too.
And check the last pages of
this thread too

Didn't have the data to do the match yet, but I doubt the rotten luck is explained by probabilities alone, likely a bug somewhere.
Probably have to seek alternate pool, bitparking used to be good but not reliable anymore. Anyone with good suggestions?
I have very good experience with Slush's Pool.