Ahimsah actually soloed this, but it's a lot easier with two healers. This is just one part of a run when I was able to get the last two tubers needed to complete the quest. On one try, I got four, and three other times we didn't get any.
We were down to just one invisibility potion, so on our last try I used my Gnomish Cloaking Device instead. Since it only lasts 10 seconds, but can be used while in combat, I ran in a bit farther than Ahimsah before using it.