That making-of video has a timelapsed 10 hour count for making a single animation sequence for a single character. From that you should be able to extrapolate the rest: a complete character taking the equivalent for as many sequences as needed.
The proprietary tools they're using seem to be necessary for generating sprite sheets like that: they're breaking frames apart so the packing in the sheet is more optimized (I think it's the sole reason for them doing that). So an artist without these tools will take much longer to pack in the same manner.
Building the animation back should require an artist as well (preferably the one that drew the animation himself); I don't think it could be done by a programmer.
If that tool does what I think it does, which is you tag pixels of a limb and the tool grabs the limb and packs it in the sheet, building the entire body back is entirely procedural - the moment each part is separated from the original full-frame the coordinates are saved in an XML or similar.
When the assets are being loaded the engine rebuilds the frames based on the coordinates of each limb in the sheet.