Can “older” item procs like:
and
Be more like this:
Reason is simple: Siphon Souls has a whopping 6 seconds cooldown (by the way, why? Spell is merely a debuffer with very little damage) and using it for RR debuff is super inconvinient. While Ill Omen once casted spreads.
+1 from me. Ill Omen is also a free damage reduction so it will help builds to become a bit more sturdy instead of picking an almost useless skill.
(This referrs mostly to builds like melee defiler that are not super-tanky, obviously).
Again, you forgot Bleeding, in this case Mythical Guillotine…
Though you still might take Siphon Souls for Blood Boil and the DA Shred from Guillotine, applying the RR is annoying.
So:
+1 from me to put the RR on Ill Omen.
Edit:
Even when you take transmuter, which results in Siphon Souls having 6 seconds duration, it is still…“not perfect”. Especially with the reduction of damage and the conversion to Aether (if you want your Vitality Damage converted to Physical…).
+1 from me. Omen it’s used in lots of builds now anyway with the damage reduction mod. So RR going to it will be more reliable than Siphon Souls - skill with long CD.
Personally I don’t agree with the change due to confusion from Ill Omen - not much fun when melee! I’d much prefer Siphon Souls gets the CD dropped by a few seconds so you can cast it more often.
Can´t say it´s not fun. And because Ill Omen spreads, it will hit more enemies than Siphon Souls (in my experience).
I have to disagree with this as a general idea for a number of reasons:
Had Omen not seen the %DR, then this might be suitable.
If Crate is up for it, it could be done on a build-by-build basis, where how many points into a mastery for any particular combo is analyzed. But that is probably getting too complicated for them.
Devouring Swarm, Night´s Chill, Spectral Wrath and Curse of Frailty/Vulnerabilty would like to have a word with you about this. 
Or this, I honestly don’t mind this (and I doubt anyone will). Siphon Souls is a weird skill. It’s a debuff + heal with 6 (!!) seconds cooldown. Having to cast it for RR feels like cancer, especially on melee builds with no cdr. So for example if Blazeheart had -2 seconds to SS cooldown, it would make Defiler (or Fire Opressor?) much more enjoyable.
yeah i dont fully understand why the aether mutator has + 6 sec giving it a whopping 9 seconds duration. compared to only 3 seconds on the vitality version. But em yeah its sticks to targets(but too short) which i really like and it affects everything in a radius which i really like. You can move and apply this to get sustain for 3 seconds. Would be nice if it would simply be 5 or 6 seconds duration so that it would last almost or fully its cooldown.
war cry also has some of these problems
Another fantastic idea from the Best Builder Evar. +1
+1
Hm. 
I am all for making it better for ocassions where its needed for RR proc. Like adding -2s cd to Blazehearts for example. But currently casting it on stuff like dual Blazehearts Defiler or Bonemonger Apostate is a little bit of a cancer.
I like SS skill but not for RR and not on 6 seconds cooldown.
But I pointed long time ago that the skill requires more damage and less CD to make sense. Still Omen is proper skill for RR since it can carry the proc throughout the screen and you already pick the skill to damage reduction. So two birds with one stone!
Low radius, huge cooldown (so it’s not readily available when you start important fights), extra button that disrupts autoattacking (because you already need Ill Omen or RE for damage reduction) and general uselessness except added RR.
I mean, overall, it’s one of the most useless and weirdly designed skills in the game, imo.
I personally hope to improve Siphon Soul (eg swapping recharges and durations), but if that doesn’t happen, I agree with the OP.
I’d leave the rr as is, add cooldown/uptime mods where they’re needed (maybe adjust dmg or adcth values if the heal turns out to be too good) and give it the WoP treatment - increase radius at lower ranks so that it doesn’t require such a big skillpoint investment.
Mastery skill base cooldowns have been steadily decreasing over the past year or so - doom bolt, canister bomb, reap spirit, etc. The recent 1.1.6.1 patch is the latest of these developments.
So now Siphon Souls and War Cry really stick out like a sore thumb compared to most other mastery skills, relatively speaking, in terms of their base cooldown (Devastation is exempted due to its power). It’s time to give them both the cooldown reduction treatment. How about making them both 5 seconds?
By now, the procedure should be routine: after reducing the base cooldown of SS and WC, find all items that further decrease SS or WC cooldown and reduce their cooldown reduction amounts.
