All of the variable caves are doable by 10th, depending on class and build. If you're talking about balanced parties, high spawn vampires are the only ones that are a problem for a party by 9th level.
Lower level parties 5th-7th level, can do most of the caves on low and mid spawns.
Below 5th level there's the traditional places. ML crypts, beetles, Zeklos, slum sewers are doable with a small party at 4th even with wererats spawning.
Thouls at high/max spawn can be difficult for lower levels, and non AC build fighters.