At least frost does, but arcane/fire keep up too. And arcane is only spec that can solo sylvanas from Shadowlands (haven’t done it, but there is a youtube video of an arcane mage doing it)
More sustain and defenses (granted its all active and you need to know how to use most of them, like alter time) than most classes.
You got strong barriers (normal barrier, mass barrier, blink barrier)
Self heal with ice block, and technically can go to ice cold and still do stuff and still have the self heal, but I find the other talents to be better (edit: actually trying out cold snap after all, I can see why most mages take it)
Displacement self heal
barriers can self heal
slows as arcane and frost
Tons of crowd control abilities as frost
alter time, takes practice to use but very good
If you add leech to that, even better
I imagine missing a thing or two, already listed a lot
Mage is honestly kinda OP for soloing. I find I have an EASIER time soloing on my mage than my ret paladin. And I can just stand there (mostly) taking hits compared to my hunter, shaman and evoker characters. My warlock can stand there taking hits, but I find mage to be a bit tankier (at least frost due to cold snap)
Mage is seen as super squishy because of how it was in the past.
but in DF it has more defenses and self sustain than hunter, warlock (maybe affliction warlock is better because all the drains and life leech), better heals imo than ret paladin, evoker, shaman, priest…hmmm…most classes tbh. Blood DK better still and most tanks still better, but for DPS I find mage to be very tanky and self sustainable.
Definitely overlooked for soloing, because how people perceive them from the past.
(to add:
There is fire cataracts think its called, thats like a cheat death sorta
Invisibility is sorta an escape death, can break aggro and give you a chance to live (does reset the enemy though)
Reabsorbtion I guess is ok, 5% of mirror image hp to heal, but only by direct damage