I assumed the OP just meant that is there an equal chance of each effect cropping up each time we rage (ie, is it a roll of a fair d8, as per RAW, or is the die weighted, either with karmic dice on or off). As you say, even with a fair die we're not necessarily going to see the effects coming up an equal number of times, which is why it's hard to know just from observation in the game whether the die used is a fair one or not.
