Wood filler or sawdust & glue will hold up OK and isn't a bad way to go but epoxy is much stronger and somewhat easier to use because it will basically flow into place & lay flat. Typically I use some flat plastic stock I have laying around to smooth it out and if I need to build an edge I put a little grease, Vaseline, or Crisco on the side of the form I make from the plastic stock that I don't want the epoxy to stick to. Something like the bolt holes I would used plastic tube with grease to keep them clear then flow the epoxy into place on top edge with cabinet standing on end - the lay cabinet on the side to do the side of the cabinet.
Epoxy was not my idea - it came to me from a guy that did high end antique furniture reconstruction - but once I learned how to work with it I don't use anything else for wood repairs. Nothing dries stronger & it is fairly easy to work with once you get a good method figured out.
My main purpose of replying to this post is for others who might read this. Not to suggest you did anything wrong using filler but to give yet another method of repairing cabinet damage. I like using epoxy for edge damage because edges get a lot of abuse but under the leg (like your repair) is a lot more protected.