I had the same situation with an 2d artist, not pixel-art but just painted stuff in Photoshop. We wanted to do an isometric game and after he started working on some characters , we came to the conclusion that he had to do not 4x times the work, but almost 5-6 times the amount of work for each character (walking cycles from 4 different angles).
The 2nd approach has to make the 3d characters and animations in 3d, paint the UV maps so they look stylished.
I think If I wanna make a pixelart game, I will first model the main characters in 3d, and make the pixelart on top of the rendered animations
A very late response. But I would say I am "not" an artist, but I can still manage a lot of stuff on 3D softwares, the tools make it possible for me to create stunning 3d models/scenes without having the creativity and knowledge that an artist possesses.
When it comes to 2d, you need way more knowledge of colours, shades, structures, shadows, movements, etc. to create something appealing. I am not taking away anything from 3D artists, but I can say 2D is way more difficult and time consuming.