Seal of Vengeance (SoV): The Seal in question.
Holy Vengeance (HV): The debuff left by Auto-attack hits/crits whilst SoV is active. This debuff causes periodic damage to the target.
SoV Proc: The direct damage proc from Seal of Vengeance. The damage of this proc depends on the number of copies of HV on the target, up-to 33% of weapon damage for 5 copies of the debuff.
A new build on the PTR has slightly improved the damage output of SoV during the ramping-up stage. In previous builds, the SoV Proc only occurred when 5 copies of Holy Vengeance were up on the target. Now, Seal Proc damage scales with the number of copies of the debuff on the target:
Holy Vengeance Stack Size SoV Proc Damage (% Weapon Damage) 0 No Proc 1 6.7 2 13.3 3 20 4 26.7 5 33
The Holy Vengeance debuff is still only applied via auto-attacks and HotR.
CS, DS and Judgement, aswell as Auto-attacks and Hammer of the Righteous, can all trigger the SoV Proc.
For the record, I still think it's a bloody stupid system, but it's now marginally less stupid. At the very least, Seal switching when DPSing a single target is totally unnecessary if the target lasts >6 seconds.