Many players already know this but let me re-introduce the problem we are dealing with in here.
(First of all, let me state that the following is not considering the default PVP spell hit cap, but only affects everything OVER such a cap. Everything you read below presumes that you are already hit capped.)
The game consists of talents such as Unbreakable Will that increases a chance to resist fear, silence or stun by 15% (5/5).
The game also consists of talents that do exactly the opposite - increase a chance to hit/reduce a chance to resist - like Shadow Focus that reduces the chance your shadow spells will resist (fear, silence, dots).
And then there are spell hit gems and buffs that increase spell hit rating. These also provide a resist reduction by %.
Now, the way the game worked ever since its initial release (actual retail TBC), the talents that reduced chance to resist/increased chance to hit + spell hit rating “penetrated” the talents that increased a chance to resist, meaning that when you had 5/5 Unbreakable will vs 5/5 Shadow Focus, you would only have 5% chance to resist all fears, silences and stuns - NOT 15% !!!
This is also how the game actually worked during the officially emulated TBC experience (Classic TBC) during Phase 1.
Unfortunately, for some unknown reason, Blizzard recently decided to break this behavior entirely with Phase 2, with a stealth/ninja change without a single mention in changelog/patch notes, which ARTIFICIALLY increased all PVP resists and made the game even dumber than before.
This is a direct NERF to spells such as:
Shadow Priest - talent Shadow Focus
Elemental Shaman - talent Elemental Precision
Mage - talent Arcane Focus
Mage - talent Elemental Precision
Warlock - talent Suppression
Hunter - talent Trap Mastery
What does this mean? As a shadow priest with 15% spell hit rating (5% from gear, 10% from shadow focus talent) you still have 15% chance to resist all Psychic Scream and Silence into a disc priest instead of 0%, which makes your shadow spec even more borderline inferior to disc than ever before.
What does this also mean? Mages will resist more counterspells than ever before, same for all warlock spells, same for all shaman spells. All these talents listed above are USELESS as they currently do nothing at all and putting any points whatsoever into them is a complete troll.
On the other hand this is a direct BOOST to many meta comps that are already on top of the ladder without even considering this boost - especially Disc PR will benefit out of this the most.
But what does this mean for the overal PVP gameplay? Yes, you guessed it right. Resists, resists, resists and even more resists. Any competitivness that the game had left is also gonna get reduced by a lot.
Resists are NOT healthy for the PVP gameplay, especially resists of the absolute key CC spells such as fear or silence. This is a mind-boggling stealth change from Blizzard and in my opinion it deserves acknowledgment of Blizzard Dev employees that are responsible for it.
TLDR: More spell resists for no reason in Phase 2, spell hit rating and certain Hit talents absolutely useless in PVP (they dont work at all above default hit cap), meta comps became even stronger, non-meta comps became even worse.
Sources (some of them are already dead in the present time) and Proof:
I cannot post links here so put this together and paste it into your browser