Example
I'm pretty sure that the greens are not better than my T6 BP. Nor are they better than my T6 Bracers, Boots and Belt (best pieces in the game) or the Sunwell DPS Shoulders. Level 60 Naxx epics are not an upgrade for a Warglaive of Azzinoth, and neither are grey sparklers.
Curiously, this bug (greens and blues being overvalued to the point of idiocy) only seems to effect plate armor. My cloak is evaluated more or less properly, and it evaluated my legs and gloves properly. It skipped the direct upgrade for my leather hat (it recognized Duplicitous Guise, which is a leather item, but skipped Crown of Anasterian, which is a plate item). That may be because you're ignoring other armor types, which would be... a curious implementation for classes that can wear multiple types, but the way in which it seems to be evaluating plate is just not working.