I'm pretty sure that a small amount of oil vapour and gas from the dipstick is normal on any diesel, and some will even blow oil out of the dipstick if it's out while running. It's not itself a sign that anything is wrong.
How long have you been getting the bad smell for? When mine does a DPF regen and it's stationary it sometimes generates a sulphurous smell - is it possible it's just happening during a regen?
It's like a hot water smell, happened twice now and again this morning, I've just posted another thread with a pic of a part where I have the oil, but it is around the dipstick.. You maybe right in what your saying just get concerned when I start to see oil