Having played Warlock allot over the years, I decided to go a Mage when classic came out.
I did not and do not enjoy playing Mage, its easier to play in PvE but i get allot more enjoyment from playing Warlock, in all content including PvE where you struggle with threat and +hit (way more than a Mage).
But this is just my personal preference, for me I just enjoy playing a Lock allot more. Even just the lack of downtime drinking is a big thing for me. Just dying in a BG, ressing, cast Ice Armor and Arcane Intellect I go below 50% mana so have to drink xD
Having mained a warlock for more years than i’d like to think about I can recommend warlock over mage.
Mage are pretty fun, got one at 57, but warlocks in my opinion is more fun.
You want self heal? Tankyness? And still have a chance to be in top 10 dps in raids? Warlock is your class!
It never ceases to amuse me watching mages get crushed in raids due to overaggro or being an unlucky target of trash mob spells, such things do not happen to warlocks, last week during a drunken BWL run I even got to tank Flamegor for a few seconds, saving us from a wipe(healers & tanks dead).
If you go mage, prepare to drink a lot.
If you go priest, prepare to wand a lot.
If go warlock, you dont do either.
Plus as a warlock, you dont even need pet, you sacrifice it and never stop casting.
Warlock is much more fun than Mage when you get geared out at 60. I love the fact you can fully DoT someone up and know that even if they kill you they are probably going to die in most cases.
The burst damage is also insane I quite often get nightfall procs and if the instant shadowbolt crits and Shadowburn also crits you pretty much one shot anyone for like a combined dmg of 4.5-5k damage. It’s even better if you go full Destro and get Conflag too.
The only class that has better burst damage than Warlock is the class I’d recommend you play and that is ELEMENTAL SHAMAN. Why do I suggest you play this?
-It’s a ranged class/spec
-Insane burst damage
-It’s a hybrid class and your Warrior friend is going to need support which you can provide in between DPSing with heals and you can also offer him WF Totem which is a major dmg increase for him.
But if you have your heart set on Mage/Lock then Mage will be the easiest path but Warlock is much more fun to play. The most frustrating thing about Warlock is:
-Soul Shards
-Lack of mobility - once Melee classes are on you, especially Rogues and Warriors it’s very hard to shake them off and Rogues will punish you hard with stun lock, you’ll need good gear and a high hp pool to survive a well played rogue.
So I’d go lock, if I were you.