You’re delusional. An AQ geared tank heading into naxx will have 30%+ crit without world buffs. To put it as plainly as possible, Shield Slam does not directly scale with anything except block value. Yes, it can crit, yes, Impale will boost that crit damage, but it is completely unaffected by AP in any way. Bloodthirst scales. That’s why fury prot is outright superior for threat under any circumstance. Flurry is the largest TPS boost to HS spam in the talent trees. Enrage is an outright better damage buff. The utility of swapping to DW for extra threat and then swapping to shield to have every bit the same inherent mitigation of deep prot is why fury prot is an outright superior raid spec.
The better the gear, the bigger the gap between fury prot and deep prot. Deep prot is for new tanks with very little gear; it’s a spec that fills in the gaps with flat amounts of threat and utility.
Consider what you’re saying when you spout off “fury prot is only better with world buffs”. What are world buffs? They’re stat boosts. What is AQ/Naxx gear compared to BWL gear? It’s stat boosts. The gap between BWL and AQ gear is large, and the gap between BWL and Naxx gear is massive. Without any world buffs and only AQ gear entering into Naxx, fury prot has better threat generation, more options to generate threat with a DW swap and Deathwish (which you’re happy to ignore exists), and loses ZERO mitigation
Stop giving people bad information. Deep prot is outscaled at the end of BWL.