Sorry that this is such a major change, but I’ve been doing some analysis on the differences between faction parses for the same classes and specs and there’s some pretty big differences.
I play a holy priest, and I kept feeling like the Alliance parses were absurdly unobtainable and consistently much higher than what I saw on Horde. So, I pulled down some WCL data via the logs, and computed the “alliance advantage”. Effectively, what I did was pool Alliance and Horde, and found the per-faction percentiles. To my surprise, for pretty much every data point, Horde has a “disadvantage” compared to Alliance.
The Alliance advantage is computed as (dpshps for Alliance parse - dpshps for Horde parse) / (dpshps for Horde parse). Effectively, this creates a comparison between the DPS or HPS which is achieved at the same percentile for each faction. For almost every class this is in the 6-12% range, and my own class (holy priest) feels it really hard up in the 99s where effectively the Alliance advantage goes exponential.
The graph effectively shows the advantage that Alliance has compared to Horde for the exact same (faction-based percentile).
Here’s the breakdown per class, for dps or hps (whichever is relevant for the role), for each boss in Naxx, for a 90th percentile parse. The blue (left column) is Alliance dps/hps for 90, red (middle) is Horde dps/hps for 90, and green (right) is combined 90 parse (eg, the current way it’s calculated). The % is the increase in hps/dps observed on Alliance parses.
For example, a holy priest on Grobbulus with a 90 Alliance parse is expected to do 348 hps, while a 90 Horde parse is a 284. Given the sample size is massive, I don’t think it’s simply noise. I think fundamentally there are some major advantages for Alliance, (largely Paladin buffs), that make it such that identical percentiles for each faction have double-digit percentage differences in dps and hps. This makes Alliance percentiles skewed up, and Horde percentiles skewed down, since the two factions are pooled together.
Let me know if you think this analysis is accurate. The advantages for Alliance are just so high, and this is shown by my Horde priest rank being ~80, while my actual priest rank is ~500. There aren’t 6x more Alliance players, it’s not something that’s really explained with play style, noise, or a larger Alliance player base (which seems to be about 30% higher total).
Edit: Updated graphs and gist as n has increased. Data covers 260k of 306k Naxx clears (trying to throttle my requests)