This is mostly just for anyone unaware, might keep it updated with any new info that arises but more or less, but here's the list of currently soloable stuff (at least from what I've done, feel free to bring to my attention what else is soloable as a Druid). Hopefully it inspires at least someone to try out some of the stuff for themselves!
Spreadsheet for anyone who wants it!
PS: Having issues with Hellfire Assault, so... feel free to tell me what's soloable there.