Don't interpret "I use it a lot, it will benefit me if the spell is changed in X way" as "I want to make my class more OP". They are 2 very different concepts. Making Stoneskin 2 instant cast will NOT break balance in any imaginable way.
Also what reason would making Stoneskin 2 instant cast make some players unhappy? So far the only thing I read on this thread is, "It shouldn't be used too often". Well in this thread I don't care about how often it uses, I only care about what happens when it's used.
And just so we are clear, I hate Stoneskin with a passion. If you read one of my old threads I created an entire thread telling people Stoneskin is way too over used. But I still recognize there are healers attached to it like dung beetle on shit. And these healers will take that 6 seconds of time casting this damn thing after I popped Fight or Flight.