Prior to the Classic Timewalking release I was able to enter those classic dungeons on a Level 70 and one shot the level 30 mobs inside. Now that Timewalking is here, it takes sometimes 3-4 hits to take down trash mobs in those dungeons on normal. All of the other classic dungeons and raids appear to be unaffected.
Apologies if this was already reported somewhere. Didn’t see a thread on it.