Since I am too lazy to check the end results by myself…
As 1.1.8.0 cut down the RR provided by mastery skills by -5%, it means that if you got RR from both masteries then you are now down by -10% right?
But if enemy Resistance only took a -5% hit, then a nerf to mastery based RR in general?
Any notable impact in clear times as a result?
Well, my DW Aether Battlemage feels much more powerful and consistent, able to farm Morgoneth 100% and reached SR 60, so I can’t complain. =D
Amazing times for my Chaos Witchblade and Warlock (especially for the last), since they do not have innate RR 
. And bad for Valguur Cabalist - -9% from maxed Spectral Wrath and flat 5 point RR from Scales, worse life sustain due to Sigil of Consumption set part nerf. Kuba, Zantarin and even Moosilauke now are truly annoying for him (I do not know how I will deal with them all at once in Crucible/SR, if alone they became harder 
).
This…mostly.
In most cases, the RR change didn’t really shake things up much. Only in situations where sizable item-based RR is/was attainable is it a potential buff over the way things were before. There are niche arguments to fringe-RR values that might make certain skills (Terrify) potentially much better than they were before, but such cases are very limited.
All in all, a step in the right direction, but just a step. Nothing more.
The difference won’t affect builds that much.
It will help some fringe builds with only one source of RR or Battlemages with none. Also should help classes without passive RR, cause you can’t RR every enemy in range, especially in Crucible. Builds with passive RR or relying on mines with mods, will perhaps take small hit.
Since you’re pet master, perhaps change will improve a bit elemental Conjurers, cause you’ll rarely have both Devils and CoF on all enemies and your pets will attack the mobs with slightly less innate resistances.
Interesting thing, that’s yet to be discussed is RR provided by gear, now these items are even better!
Personally, I am looking at it like a straight up buff for Ghol Pet Ritualists 
This goes for pet builds that didn’t get much in the way of RR as well like Chaos Conjurer that relies entirely on gear/devotion for sources and more meme ones like Elemental Druid/Warlock or Aether Spellbinder that just have 1 mastery source.
You’re right, I didn’t considered chaos pets buffs. Maybe will try the in future one legendary 2H chaos pets weapon 
Ok, so after testing things out a bit…
I don’t like this change 
Healers have got more annoying, Superbosses have got more annoying, Crucible has become nothing less than a pain…
My pets took a decent hit 
Note: Ghol is still doing just fine, especially Ritualists since their RR comes from devotions and skill modifiers + Pet aura rather than masteries. Ironically the one pet build that didn’t need more dmg, got more damage…