Much in the same vein as this question, I am trying to convert 5e so players roll all the dice. I'm using this variant as a starting framework that seems to work well with 5e so far, without changing monster vs. player statistics.
My stumbling block is spell saves. Take a humble goblin and his +2 dex vs. a high level save of 19 (8+6+5). He has a 4/20 chance of passing that save. If I stick to the same-ish formula of 14+2 vs. (caster mod)+proficiency on the players’ side, I end up with the goblin having 4/20 of saving.
I am looking to convert spell save DCs from 8+proficiency+caster mod vs d20+ stat mod+proficiency fairly. I think 14+saving throw does so correctly, and fairly. If not I want someone to tell me why that’s wrong.