When PRR was first introduced it gave heavy and medium armor a small advantage for its use, you had more PRR than the other armors. Now with the dodge changes and new enhancements to gain prr the pendulum has swung back in the other direction. There is no reason what so ever to wear medium or heavy armor. The gain in PRR does not balance with the straight miss chance a dodge 10% item gives.
First we have to look at robe using characters and see what kind of damage reduction and miss chance they can achieve.
Dodge 25%, Blur 20-50%, Incorp 10-35%, AC small percentage but in favor of robes here with wisdom to AC and no cap in dexterity
PRR = 0
PRR sources for robes: Epic damage reduction 10, Eldtrich Knight 10, Mountain stance 15, Blue socket 16, Shinato 15, Epic Destiny Grandmaster of Flowers 15
Heavy armor bab20:
Dodge 1-5%, Blur 20%, Incorp 10%, AC small percentage
PRR = 26 or 15% about
100 Attacks, 200 damage attack at base #'s not counting the differences in blur or incorp and considering AC to be about equal to negligible.
35 hits for 200 = 7000 dmg
Heavy armor at 5% dodge
65 hit for 200 = 13000 - 15% (1950) = 11050 dmg
Real simple math here and it only gets worse as the robe users adds other sources of concealment or incrop and PRR. Adding massive amounts of PRR to actual armors could help but the what would the amount be just for the baseline? 40% reduction which is 80 PRR!! away from the original 26 put the baseline at 7800 damage. This is how drastically big the dodge advantage can be over armors.
So how to fix?
Make each armor type have in the hit formula give a guaranteed % of glancing blows. This is like AC in a way but it would be unmitigatable. So light armor 5%, medium armor 10% and heavy armor 20%. Have shields give more to this number and maybe increase how much they reduce glancing blow damage by 10% small, 20% large, 50% tower. If your wearing armor you should take blows better and PRR is not going to cut it because robe users have access to enough prr as is and with diminishing returns makes it so you cannot catch up to the same mitigation.
So example -
20% blur, 10% incorp, 5% dodge and 20% glancing blows from heavy armor, 100 swings at 200 damage:
20 x 200 x 20% glancing blows from armor = 800
45 x 200 x 15%(1350) full hits = 7650
8450 total damage a bit better but still not at the same level as no armor
Option 2, change the PRR scale to favor more past a certain point, this would only work for shield users who can reach higher PRR, heavy armor only has a 26-30 prr advantage over robes, non monk which they can match
Option 3, make enhancements that increase the dodge cap of heavy armors, not this +3 to max dodge that is way to small should be 10 to adjust to the new system. This is an easy fix and maybe the combination of the glancing blows and higher dodge it will put heavy armors back where they should be, in the front lines taking hits.
Robes should be quick and get hit less, heavy armor should get hit more but for much less making it a desirable target to heal as the damage is not as spikey yet competitive with the mitigation. PRR doesn't solve this. AC doesn't solve this.