As a point of reference, these are the uptimes and proc rates we can expect from each version of the Rune of Re-Origination:
Heroic Thunderforged (541) - 1.14 RPPM - 38.08% uptime
Heroic (535) - 1.08 RPPM - 36.00% uptime
Normal Thunderforged (528) - 1.01 RPPM - 33.67% uptime
Normal (522) - 0.9569 RPPM - 31.90% uptime
LFR (502) - 0.7943 RPPM - 26.48% uptime
This is based on the original 0.92 RPPM value, the 10% buff which makes it a 1.012 RPPM, and the various RPPM multipliers which are posted
here.