I've killed Moder solo and ye had to kill the Elder with arrows while avoiding attacks. It's not the worst thing honestly as while you need to level your gear more than other it can be done, though I've not tried Yogg yet... heard his regen could make it actually impossible.

Though ye death runs could do with a little work, even if you are lucky and built a portal nearby it can still be super hard to get your stuff back depending on what killed you. I'm starting to just chain portals together into a huge jumbled mass so I always have 1 close to where I am currently.