A better option than it as it was. If this slight reversion doesn't fix the problem, then I think you should consider increasing the percentage where the curve changes, and making the penalty curve harsher. Such as, until 20% stamina it's the original curve, then instantly drops to 50% decreasing to 1% at 0% stamina.
I'd also be interested to see how bots are affected by the update, because whilst alts will be, bots can simply change their script to not reach low stamina. Jagex will have better data on how much excessive ore flooding in is bots versus alts, but in F2P at least, I think a majority of it is from bots rather than alts.
Yeah bots isn't really a problem I can deal with from a design perspective. I leave that to the bot detection department.