As the title says I suggest to rework Soul Siphon to change Drain Soul to the WoD version of the spell.
Meaning:
- Drain Soul damage is increased by X% and can crit.
- While Drain Soul is active it increases damage of your affliction damage over time spells when target is in execute range (20% and below) by 100%.
- When Drain Soul deals damage, it causes all of your other damage over time spells on the target to instantly deal X% of their normal damage.
This would help make the rune better as a pure dps rune for Affliction, changes the play style away from spam SB until you recast a dot and give Affliction an “Execute” style-ish ability that finally is more viable than Master Channeler.
It would not be op for pvp because you are fixed in place while channeling Drain Soul and can be easily interrupted from range or melee to lock the Warlock out of using any shadow damage spell which as Affliction is basically all of them.
And it replaces the single strongest selfheal the Warlock has because it’s on the same spot as Master Channeler.
An alternative would be to keep Soul Siphon as is (maybe add Drains can crit) and make Dark Pact the capstone for the Affliction Tree change Drain Soul to how it worked in WoD.
And since it would replace Ruin you could add that Nightfall procs apply the ISB debuff without charges on the target while Drain Soul deals damage.