I do think that this would work as a tier, but I disagree with it being only characters with 0 Joules or whatnot. Like has been brought up, this is essentially impossible if you're 3-D, and would need actual evidence, which I doubt any verse actually gives, making it obsolete.
I believe Low 10-C should be closer to Jaftens proposal, with characters / entities who are artificial or negligible in most cases on a 3-D scale. This would be programs, viruses (Both computer viruses and biological viruses), and probably cell scale stuff.
However there's still the fact that programs and such, don't
actually have energy. Sure, they are composed of electrons and such, but the electrons do not define the character. They still pose no threat to anything other than what is on their level. A cell has infinitely more of a chance of killing you with striking strength than a computer virus does, because it can actually affect and interact with you...
Due to this, these digital/artificial beings would be somewhere even lower, somewhere below the previously defined Low 10-C, but above 11-A, as they are still 3-D.
Perhaps High 11-A is in order too? Characters like this would include the likes of Programs, Computer Viruses, Drawings, Artwork, and more imo, as these all share the same traits of only being notable threats on their own level, but still exist on a 3-Dimensional Axis.
TL;DR: I think it should be along the lines of
- Low 10-C: Closer to what Jaften Proposed, however I'm not sure whether to draw the line at 1 Joule. This would include Cells, Biological Viruses, Bacteria, and anything actually capable of interacting with other 3-D objects.
- High 11-A (Or whatever it could be called): Digital/Artificial Beings such as Computer Viruses, Programs, Drawings, Paintings, etc. That cannot interact with the 3-D world around them as they're bound to their own world, but are still bound to the 3-D world. (If that makes sense...)