[DemonHunter] Voidfall proc rate is stack-dependent (per-spec)

[taherbert]

Summary

• Voidfall building proc chance decreases with current stack count, rather than being a flat rate from spell data (effectN(3) = 35%)
• WCL analysis of 72k+ eligible casts shows per-stack rates with high statistical significance for both specs
• Devourer procs ~2pp higher than Vengeance at all stack levels (z-test p<0.02), so each spec gets its own defaults
• Defaults exposed as per-spec player options for tuning

WCL Data

Vengeance (21,942 eligible Fracture casts, 325 players, S1 live)

Stacks	Eligible	Procs	Rate	95% CI	vs 35%
0	9,591	3,677	38.3%	[37.4%, 39.3%]	p<0.0001
1	7,471	2,432	32.6%	[31.5%, 33.6%]	p<0.0001
2	4,880	1,457	29.9%	[28.6%, 31.2%]	p<0.0001
Overall	21,942	7,566	34.5%	[33.9%, 35.1%]	p=0.11

Chi-squared: X2=121.6, df=2 (p<0.0001). Defaults: 0.385 / 0.325 / 0.30

Devourer (50,067 eligible Consume/Devour casts, 107 players)

Stacks	Eligible	Procs	Rate	95% CI	vs 35%
0	9,658	3,974	41.1%	[40.2%, 42.1%]	p<0.0001
1	22,638	7,712	34.1%	[33.5%, 34.7%]	p=0.003
2	17,771	5,747	32.3%	[31.7%, 33.0%]	p<0.0001
Overall	50,067	17,451	34.9%	[34.4%, 35.3%]	p=0.71

Chi-squared: X2=288.5, df=2 (p<0.0001). Defaults: 0.41 / 0.34 / 0.325

Cross-spec comparison

Stacks	Vengeance	Devourer	Delta	z-test
0	38.3%	41.1%	+2.8pp	p<0.0001
1	32.6%	34.1%	+1.5pp	p=0.017
2	29.9%	32.3%	+2.4pp	p=0.001

No clean formula fits the data -- likely hard-coded server values.