I have crafted 100 Apprentice arm bands (tier 1)

Of those 100 arm bands, 7 proc'd blue, the rest were green.

Of those 7 blue Apprentice Arm bands, 1 proc'd purple at the next tier combine. The remaining 6 were blue tier 2 armbands.

Based on the meta circling about rare proc's and the tier system, coupled with my own bad luck, it seems like XL games doesn't know how to hard code probability. Statistically, the rate on a population of 100 samples is a 1 in 14 chance to proc rare or roughly a 7% chance. That being said, taking 7 blue tier 1's and turning them into tier 2's, I had a 1 in 7 result, which is not 7% probability of proc'ing a rare.

No one knows if your skill level or if the current base item being used in the tier up combine is affecting the probability of a rare procing on a combine. At this point its a giant crap shoot of "Come on baby, daddy needs a purple..."

Don't make me have'ta Troll ya Bro!