I was reading an article today about diminishing returns
This isn't the one but basically even for DK's parry diminishing returns is huge compared to dodge.
You would probably have a lot more avoidance with dodge over parry if you are trying to max out your avoidance.
Quoted from the third page from Zephyr
Personally though I went for an effective health type build stacking pure stamina whenever possible.Dodge vs Parry:
With talents and base values you should have 10% dodge and 10% parry, atleast for warrior/pala these are not included in diminishing returns.
So for it to be worth it gemming for parry you will need to have more
10% parry: you need more then 20% dodge. (base)
15.6% parry you need more then 31.2% dodge. (uncrittable)
17.5% parry, you need more then 35% dodge. (normal stats)
20% parry, you need more then 40% dodge. (high stats)