The intermittent position isn't very intermittent. The delay is speed dependant and to be honest, unless you are toddling along at 20mph or stationary there is very little difference between intermittent and low speed. Not really any great benefit that I can see.
What do you mean by "normal"?
What I thought was normal, assuming no rain sensor is - off, intermittent, continuous and fast. in all cases the speed changes below about 5mph and adds a time delay between wipes.
This is on my 2010 SW but is the same as my previous 2002 307 SW.
A variable wiper control would also need a software option which just isn't available on the 308 that I am aware of. I have a manual variable control, it's the single wipe achieved by moving the stalk down as & when needed. The delay between single wipes changes with the conditions