The direction you’re going with tanks being tanks in phase 4 is brilliant and I support it fully. However, some things needs to be tuned or the dps-tank hybrid meta will stay the same and I’m not a fan of this, it’s not in the classic spirit. If I wanted to play a defensive dps, I’d play retail. In classic tanks should be tanks with defensive stats and defensive talents.
Protection paladin needs 2 things to be good and fun: Shield of the Righteous so we can do 9-6-9 rotation and some form of damage reduction cooldown and on PTR we got exactly this, which is brilliant. However, other alternatives are much better and will become the meta forcing us to play a boring dps build. This is not fun tank playstyle in my opinion.
My suggestions: merge Mallable Protection with Guarded by the Light rune, this will allowe us to once again use Sheath of Light and not have to worry about using a worse option and encourage a utility rune on feet instead of Art of War which is in my opnion meant for retribution paladins since it requires high crit chance to work well.
Also reduce the cooldown on Holy Shield down to 8-9 seconds (as it was in Wrath), currently it’s 10 second cooldown and 10 second duration, there needs to be a slight window of the buff lasting longer than the cooldown. This also gives us the opportunity to do a 9-6-9 rotation (which looks like this: Judgement → Shield of Righteous → Consecration → Hammer of Righteous → Holy Shield → Shield of Righteous → Judgement → Hammer of Righteous → Consecration → Shield of Righteous → Holy Shield → Hammer of Righteous → repeat) this is a very fun rotation and there’s a button to press every global cooldown making it engaging playstyle. This will come natural to anyone that played paladin tank during Wrath expansion.
Exorcism for protection paladin should not be part of the roation but rather initiate threat on pull or help with getting aggro on the mob far away “Steve” pulled in the back.
I apologize in advance for being bad with writing but I appreciate you reading my feedback and considering it. I only want whats best in terms of fun and viability in a raid composition for protection paladins. With these small changes, protection paladin will be a complete spec and a great class to play having a fun rotation, rewards for gearing/specing defensivly and a proper set of utility.