Love everything about my Spriest aesthetically. Got him to 54. But when I pull 3-4 mobs I almost die. It’s very different from Destro Lock where I drop Catacylsm, Channel Demon Fire, Rain of Fire. I don’t really understand the Sprist AOE - so please teach me!!
Also, will I be casting fears and stuns and shadow mend no matter what when pulling 3-4 mobs? Thanks!
Levelling I used misery and focused things down one at a time with dots on everything. Pulled big when I had cds like PI and Voidform available.
Shadow has a lot of single target damage, use that to plow the mobs down one by one as the rest weaken to dots + ghosts over time.
Be liberal with voidform. It’s on a 1.5 minute cooldown. Take Surrender to Madness for questing and dungeons because it’s a second voidform.
Dot up everything with misery, voidform, watch as your shadowy apparitions destroy everything you dotted. Also be sure to grab the one conduit that buffs the apparitions.
Ancient madness
And 2 of Lasting Plague or Void Shield or Void Origins
Fight things 1-2 at once till u got Void form will be on like 35-50 sec cd,
Pool insanity
pull 3-6 with VT (embrace depending on number and difficulty)
SN SN
Shadowcrash
Resume 1-2 at once till voids back
With 3/4 mobs, you take them down 1 by 1.
Dot them all, st, refresh dots, st another. Rinse and repeat until all dead. You could go into voidform but it’s normally not necessary.
Look at my talents, I find it optimal for my taste for questing ( and pvp lol )
You could switch aus.spi to shadow crash 
I personally use Shadow Crash. Auspicious Spirits just seems too weak for fighting normals compared to the front-loaded damage of Shadow Crash but I’d love for someone to prove me wrong on this so I can get another ability off my bar.
After dotting or multidotting, use Mind Sear instead of Mind Flay as it hits all enemies. Cast Void Eruption whenever it comes off cool down. Keep reapplying Power Word: Shield. Keep healing yourself or use Vambric Embrace as it will heal you as you do shadow damage.
If the mob damage is high, dot everything on the pull. Hit a mind blast so everything takes it. Fear and void torrent one down quickly, then devouring plague two as they come back. Pop void form and move on.
Tab dot each one and either pop Void Form and/or just cast like you’re doing regular damage. In Void Form you want to pop Void Bolt on cd, cast Mind Blasts, and Devouring Plagues you’ll send out an army of ghosts at everything around you.
Don’t listen to the bunch of newcomers.
Anyways, if you’re gonna go in packs of 4 or less, go with misery. In case you wanna hard aggro, especially with fleshcraft, go for searing nightmare (i play it anyways, way more effective than spirits)
So, void torrent first to have some insanity to spend, vamp touch all mobs if there are fewer than 4, then voidform, mind sear + shadow crash 3-4x. If the mobs are weak, just aoe shadow crash + min sear + searing nightmare.
If you’re gonna run hard aggro, i recommend using D&M as first talent, since it grants you repeated executes and replenishes a LOT of insanity
EDIT: Why 4 or more? Because it’s a waste of gcd when there’s 4 or more to tab dot with misery, since searing ramps up faster. and waaaaay faster.
If it makes you feel any better I didn’t find leveling spriest at all, difficult at times. I don’t usually start enjoying shadow until cap level when you start getting geared. Priest is very very gear dependent.