I've soloed every last aetherite in the game, it is possible.

Ultimately its done by stacking defense and abilities, and exploiting the tethering of monsters every chance you can.

Rule 1: Best defense possible. If in a group, heavily armored Gladiator is preferable to lead the way, with a potent Conjurer in tow for buffs..

Lead can use: Stoneskin II, Shock Spikes II, Protect II, Shell II, Defender II, Rampart II, Sentinel, Deflection (optional), Quickstride (optional)

Your main task is to look for safe zones where monsters dont follow any further, and you are not gaining aggro from stuff ahead. Obviously a good time to wait on cool-downs and rebuff.

Sometimes, however, this alone is not enough. There may too long of a path, full of stuff that can one-shot you. The solution here is to exploit the tether. Gather and train as many monsters as possible, as far down the path as you can go, till you die. Rinse and repeat. Within 2-3 deaths, you should notice that the monsters will be hanging out near the edge of their own roaming area, so when you run past them, they have the potential of only hitting you one, even zero times, thus allowing you to progress further without dying.

Raptors, Hogs, Efts, Gnats, Drakes: Best results occur (minimum hits dealt to you) when the monster is facing away from you as you run toward/past it. I know some aggro to sound, but my observation stands.

Eyes... ugh, eyes. I like to pop my defensive skills, use emulate/quickstride, and race to the safe zone by the aetherite.