Post by Heckler
Diminishing Returns (DR):
(
Source to peruse)
Everything I'm about to say is explained much better in the thread above, here's a druid specific summary:
Dodge% diminishes as a whole, after the total dodge is figured from dodge-rating, defense-rating, and agility (not as individual components). Agility, DodgeR, DefenseR all add constant amounts of PRE-DR dodge% (these values can be found in the source link above), then at the end, the diminishing returns equation is applied to find ActualDodge:
116.890707 * PreDRDodge
ActualDodge = -----------------------------
PreDRDodge + 113.6178
There is also DR on Miss%, but since we only get miss% from defense, and we don't 'stack' defense, it is negligible (Low amounts of miss actually GAIN % because of DR, explained on EJ thread). This means that the Miss+Dodge added by DefenseR will eventually be worth MORE avoidance than the dodge added from Agility or DodgeR. This happens somewhere between 50 and 55% POST-DR dodge.
This is a moot point however, because once you pass ~40% unbuffed dodge, Stamina becomes the better stat for survivability.
Agility is better to stack than DodgeR because it adds Armor. This means in total effect on TimeToLive, Agility is always better than DodgeRating, even though DodgeRating adds more dodge% per point (Since they diminish together at the same rate, DR does not come into this comparison, except in that the constant Armor/Point of agility does not diminish in this context).
Because of this, 'stacking' DodgeR OR DefenseR is never the right thing to do. By the time DefenseR becomes worthwhile, you should already be focusing on Stamina.
Basic breakdown for 'Stacking' -- Agility until you're over 40% unbuffed, then Stamina.
EDIT: As far as your expertise being 'too high' -- 10% is a decent 'too high' value for expertise (even though it doens't really 'cap' until like 16% for some bosses due to high Parry chance), this happens at 40 Expertise -- So 18 is not too high, it may even be 'too low' since its not even over the dodge cap.