I know mana is still a thing. It matters to healers in both PvE and PvP. It matters to Arcane Mages (but it acts like any other resource bar mostly). The line ends there though.
All other dps specs don't use any mana at all. The hybrids "use it" but it is just used for your heal spells, you can go out of mana and still DPS.
This has lead to a bunch of spells being so horrible in PvP that they got removed. Spells I thought were really fun and interesting. Spells like Drain Mana, Mana Burn, Mana Tap and Viper Sting.
It has also lead to a bunch of PvE spells being way less impactful like Mana Tide Totem, Mana Totem, Blessing of Wisdom, Mana Tap +++
These spells used to help both Healers and mana DPS users.
And because the mana dps users got DPS boosts from abilities like Mana Tide Totem, they balanced this with melee having other ways of getting more DPS via stuff like Windfury Totem, Blessing of Might and Strength/Agi totems.
So, why was mana changes into what we have today?
I personally see it as something they did just to reduce complexity in balancing. Like a potential mana using DPS running out of mana in the GOGOGO M+ mentality, can't have that can we?
We all moan that the classes feel boring and I think mana mattering is something that would make the game more fun. It's fun to be a Shaman being loved for giving mana to your Shadow Priests. It's fun to be the Shadow Priest that gets that extra mana and can do some sweet DPS.
Maybe reintroducing mana will not make the game more balanced, but balanced does not mean fun?
What do you guys think?