As a general rule when this warning activates it's time to hit TOGA and get out of there.
Not necessarily! There are different situations. The first is where ATHR is lagging behind due to turbulence etc. That is where one could use manual thrust to reduce the variations. The second situation where the flight path is shallow with gear and full flaps, high LW. Here the thrust would already be at CLB and only way to check speed reduction is to increase descent. This warning is likely to come in normal circumstances in manual thrust where speed is not properly monitored.