Lets be practical, for a too slow ascent rate to be dangerous it has to be so slow that you would basically not even be ascending.
A fast ascent rate creates way more problems than a slow ascent. If you ascent too fast you increase chance of DCS and the faster you ascent the harder it becomes to control your ascent rate.
Do people know where our ascent rates come from? 60feet/min or 18m/min ? It was becuase the US Navy wanted their divers to come up as fast as possible (and still be safe). The commercial divers used to do 10feet/min or 3m/min.
And rates where increased not necessarily because slower was unsafe, but because the sooner someone is out the water the better, so we keep trying to find the fastest way to get people out safely. Not for recreational use, but commercial and military.
Historical ascent rates:
Historical guidelines as to rates of ascent are pertinent. In the 19th century, for example, the French physiologist Paul Bert in 1878 quoted rates of 3 feet per minute and the English physiologist John Scott Haldane in 1907 recommended ascent rates between 5 and 30 feet (1.5 and 9 meters) per minute. From 1920-1957, rates of 25 feet (7.5 meters) per minute were recommended. Then in 1958, Cdr. Francis Douglas Fane of the U.S. Navy West Coast Underwater Demolition Team wanted rates for his frogmen of 100 feet (30 meters) per minute or faster.