Take this with a grain of salt, but a couple of weeks ago I read on reddit that someone (or group) was working on a "fix" where it would store the dag in the normal system RAM, and then just stop and restart mining every 60 seconds (or however long it takes for the throttling to begin), then copy the dag back into the GPU memory, rinse and repeat
Pretty sure I read the nerf is instant, the mining programs lag with the output they show.
Nvidia isn't stupid.
It depends on the miner. Some miners average the hashrate so it smooths out the variations, others
will show the near instantaneous hashrate which will show a drop immediately.
It's also why competing over a % hashrate here or there is silly.
Regarding your second statement, I'm not sure I agree considering the current fiasco.
If the DAG copy technique works it give a clue to how the gimping is implemented which could
lead to a more elegant solution.