I've been involved in the Theorycrafting thread over in the official forums and thought I might share some of my findings. Please be gentle.
First, HtL's uptime is easily modeled by
H = 1-(1-p)^(10/a)
is your parry chance, a
is your attacker's attack interval (i.e. number of seconds between attacks), and H
is your time-averaged uptime for HtL as a percentage of the fight. Simulation bears this equation out, though it will obviously be much more erratic for shorter fights than for long ones.
Second, thinking about block/dodge/parry in an abstract sense, they all contribute to whether or not you can be hit by a full attack or not.
Dodge and parry result in no damage, while block results in 40-70% of the damage you would have taken without mitigation, before armor and other absorptions are factored in. It is always better to take a lesser hit than to take a full one. Mastery increases Block at a faster rate than dodge/parry rating increase dodge/parry. Consequently, until you attain sufficient block+dodge+parry+miss to avoid all
full hits, mastery is substantially better than dodge or parry per percent avoidance provided. Mastery can not (currently) exceed 40% of your unreforged, combined dodge+parry rating, so that provides a hard cap on how much mastery you can have, given your current gear. The remainder should be split almost
evenly between dodge and parry, with slight (<10%) favoritism given to parry due to HtL.
Once you have sufficient avoidance to not be hit by any full hits, mastery immediately loses all value: it is always better to take no
hit than to take even a mitigated hit (no, I'm not talking about the value of EH here; that's an entirely different matter). As such, mastery should only be used at this point to ensure one remains unhittable, and all available points should then go toward dodge/parry, maintaining the same ratio mentioned before.
Here are some example cases (also posted on the WoW forums):
Using 1750 rating points...
Best avoidance: 15.8%, 15.32%, 48.79% (84.92%)
Using 2000 rating points...
Best avoidance: 16.92%, 16.61%, 51.51% (90.04%)
Using 2500 rating points...
Best avoidance: 19.18%, 18.86%, 56.96% (99.99%)
Using 3000 rating points...
Found an unhittable configuration!
Avoidance: 24.7%, 25.17%, 45.25% (100.12%)
Damage taken: 23.13%
A few caveats:
- None of those cases actually add up to the number of rating points they claim to use, because I'm simulating in hops of 10 rather than hops of 1 to speed things along. The actual values will be within 10 rating points of those.
- I'm also not 100% certain about my damage taken calculation, which will ultimately influence nothing in terms of weighting dodge/parry/mastery against one another.
- Parry rating may not be as important as parry itself, because of the contribution green strength now provides to parry rating. You can reforge gear-derived parry rating, but not gear-derived strength, so the amount of parry you can actually shunt around is likely going to be smaller than the amount of dodge you can shunt around.
I hope this is useful.