So can someone tell me why Healer can easily run out of mana especially during Tyrannical boss fight and dps like mage , lock and every dps who use mana are always full and never need to worry about that ?
I find it unfair to need to manage my mana , bring mana pot and use a CD like mana tide totem to regenerate mana and no dps class need to do any of this .
how that suppose to be fair to healer class in general ?
dps mana are always full because they rarely ever use it. and the % goes up faster because they dont have more than a fraction of what a healer has. you gain like 10% mana. but thats like the entire DPS mana pool. they have a hand full of globals that they can use before its tapped out.
Healer mana serves twofold purpose.
Whereas the skill expression for DPS is in a (usually) more complex rotation while managing additional resources like Soul Shards, Insanity, or procs like Hot Streak/Icicles.
The only reason why DPS even have mana is because it’s a limiter for utility. Instead of putting Spellsteal or Shadow Mend on a cooldown, or just making those abilities really week for DPS, they can make them strong and spammable, but the payoff is that you can only use a couple before mana regenerates.
Same reason why you can’t Innervate an Arcane Mage. Despite both being called mana, they’re very different resources and the game treats them differently.
Warlocks use mana? That’s news to me!
yeah, it exists. but idk if i would call 1% mana cost on a 30 sec CD a real mana drain.
or a 1% mana cost on a 12ish second CD or a 2% mana cost for an ability that lasts 12 mins… just stuff off the top of my glance at it. 
Because that’s what healing is about. You manage your mana to keep people alive. Magical dps don’t need to use mana anymore because physical dps never needed to either. Nearly all dps specs have some other resource to keep track of other than mana anyway.
A dps’s job is to do enough damage to end an encounter while avoiding damage themselves. It’s not like classic where you burn through all your mana and then just stand around auto-attacking while you wait for it to regenerate
It’s also because limitless healer mana would trivialize longer encounters. They can simply spam their biggest heals to keep people going for as long as possible.
Mana does generally serve a purpose for some dps specs. Like off healing. It takes a lot of mana up to throw some heals out, and it balances out because often a dps’s quick heal can be more potent than a healers.
I remember when my lock used to run out of mana and would need to life tap. Days long gone.
I find it odd that you’re running out of mana on any tyrannical boss fight. What exactly are you pressing?
You mean healer vs Arcane mage mana?