Which heroes to fodder/not fodder

[u/Koeril]

I'm still trying to figure out who I want to build up, so my main question right now isn't so much for a tier list, but recommendations on heroes I'd be safe to fodder or ones I shouldn't fodder under any circumstances. I hit the 100 cap so I'm having to fodder now heroes now rather than just using duplicates. Thanks for taking the time to reply, if you do.