Chaos Bolt and Lava Burst are essentially making reactive healing impossible. These 2 spells in particular power leveling, due to the incredible amount of damage that they can do with minimal setup (immolate or flame shock), can do... I hate to be cliche... but quite literally OVER 9,000 damage on a routine basis without any sort of PvE gear stacking involved. Chaos Bolt in particular seems incredibly problematic right now because there is almost no defense against it. If you are ever below 40% hp or so against a destruction warlock, you can basically die if they ever channel a single chaos bolt on you unless you can somehow immune it. Was not Vindication nerfed because they did not like players competing with effectively 60% of their health pool?  Tuning both of these would go beyond my scope of suggestions as I am sure it would involve a lot of number balancing and compensation but the raw burst potential on these spells is absolutely ridiculous right now and definitely needs to be looked at. power leveling is not an easy job.

Unholy Death Knights should not have an infinite supply of instantly-summoning pets at their disposal. Every other pet class has to micro-manage their pet to make sure it does not die because there is a risk involved with warlock and hunter pets dying. For Death Knights, there is no risk. Therefore, base ghoul summon cooldown should remain at 5 minutes but should also have an 8-second cast time. Unholy talent Night of the Dead should reduce the summon cooldown to 1 minute fully talented and reduce the cast time to 4 seconds. This would make things a bit more even about power leveling.

Retribution Paladins should have to "build up" their burst just like any other class. DK have to apply diseases, Warriors have to build up rage, Rogues have to build combo points, etc etc. Ret paladins just unload and can swap very freely and make anyone a potential and viable target with the ability to kill almost any class in a swap if they can not trinket HoJ. Vindication was a good start, now you just need to force them to have a build-up for their burst.

Protection Paladins absolutely do not need 2 talents that reduce the cooldown of Hammer of Justice. Not a single PvE tanking paladin will spec into the regular Improved Hammer of Justice talent and will only get Judgements of the Just for the attack speed debuff portion of the talent power leveling. This is the single most reason why "Prolydin" 19/52/0 (and variants thereof) are ludicrously viable. No one should be able to perform ranged stuns that last 6 seconds long every 20 seconds, period.