Some suggestions for casters:
- Change Intensify Spell Metamagic to +5 caster level and max caster level, Passive: +2 pact and blast dice and 140 spellpoints.
Gives it seperate identity to Empower and makes it more relevant in epic/legendary levels where you'll have much more spellpower, the passive pact and blast dice make up for the fact warlock blasts do not benefit from caster levels.
- Add feat Legendary Metamagics for 30+
"Each of your metamagics cost one less and you gain an always active bonus for each these metamagic feats you have
Quicken Spell - Gain 10% spell cooldown reduction.
Empower Spell - Gain 1% spell crit chance.
Maximize Spell - Gain 10% spell crit damage.
Heighten Spell - The maximum caster level of your spells is increased to 20 before all other increases to Maximum Caster Level
Intensify Spell - Gain 10% spell cost reduction.
Embolden Spell - Enemies no longer automatically succeed a save on a 20 against your spells."
Doesn't have to be these effects specifically, just something to help metamagics that feel massively impactful in heroic levels feel a bit more relevant for their feat cost when you're pushing over a thousand spellpower and DCs well over 120.
-Rework the Master of X feats besides Master of Knowledge
A lot of the master of X feats are awful as a consequence of just increasing the maximum caster levels of spells that are bad even with the bonus, hell Master of Poisons is in the running for the worst feat in the game (+10 caster levels to a terrible MCL 20 spell sure does a lot and +5 damage per tick to wave of poison...)
Make these options to give immunity strips to casters through the feat system if they're unfortunate enough to have not been given a strip through class levels or enhancements, make each one an SLA of about 6th level with a 10 second cooldown 20 second duration much alike the Chaosmancer racial SLAs
For example
Master of Death: Blast an area with overwhelming negative energy, all enemies hit lose immunity to negative energy damage if they have it and take d6+6 per caster level in negative energy damage.
It'd also serve to give another spell option for casters who don't feel they have quite enough to build a full rotation.
-Unkill Carrion Swarm
As the the epic strike most designed around sustained damage it's sad that even with maximized DCs there is always at least a 5% chance you'll drop all stacks because a target saved.
Change a saving throw on Carrion Swarm from dropping all stacks to simply negating the damage for a tick.