You may be able to solo the first boss and second boss, the ash titan is going to mighty difficult solo. Maybe with a sorc shield stacking heavy armor and pets you can whittle it down, but both adds and the boss on you will be nuts to mitigate/shield that much damage.
If you're looking for "end-game" solo content, I'd suggest the group delves in Craglorn. They present a pretty decent challenge for solo players, especially the ones in Upper Craglorn.