I think the main culprit here is the fixed mishap table where all mishaps are equally bad, which forces the introduction of the convoluted safe casting rules. I wish they had simply made the roll for mishap/overcharge based on power level and had a table or mechanic where the worst mishap results were only possible if you rolled many (like 3+) mishaps at the same time. I think that would have been much easier to write and would have made more intuitive sense to a large amount of players.
I use such rules in my game just because it was very difficult to introduce those rules to my players-mages. I've created new mishap table with more severe injuries but now it depends of power level of spell tightly.
Could you post those? I was thinking of changing the mishap table to have (say) 15 results just numbered from 1-15. You roll a number of D6 equal to the nunber of mishaps you rolled and add them together. Thus if you only got one mishap, you would get between 1-6 on the table. Two would give you from 2-12, and 3 would give you 3-18. The top result would be the 15+ which is the "you ded" result, but to get that you have to get 3 mishaps on a spell AND roll 15 or more on 3 dice, so it's a lot less likely than 1/36. I haven't actually DONE this yet, just been idly thinking about it, would love to see what you did.