Logged into my account after the update and my level 67 Warrior is now level 1.
Also my other low level alt is gone.
Should I just wait and it'll be fixed or did something major happen?
The character on which you are posting, Legomyaggro, is presently active as a level 67 Night Elf warrior. With this character on Dark Iron, rests a level 32 Night Elf druid, as well.
Were you perhaps logging into Gorefriend, my friend? I'm showing a level 1 on that realm by the same name as your warrior. :)