Druid + Necro Root Rot locations

[Defo]

My friend has come back to p99 and rebooted his 57 necro. I am a 53 druid. I have been charming bats in Sol B, and root rotting Yeti's in Dreadlands for some more casual exp -- but:

We're seeking a location where we can stack up DoTs on mobs and root rot together. He does not want to charm. We tried Sol B, but the bats are too low HP and not great tanks versus the spiders.

We had some success in City of Mist ramparts, but he claims the exp is a little slow for him at 57.

Are there any locations you can think of that would fill this niche? (Elsewise, I'm going to convince him to stay in City of Mist, because it's easy to manage the pulls with harmony)

Or maybe Karnor's basement?