How long does it take to dry your hair?
We have had a 30 amp RV now for 7 years (2007 Winnebago Outlook 31C). To use a blow dryer, you HAVE to turn off the A/C and the electric water heater element. It is only for a few minutes though, so it isn't an imposition.
We also have to turn them off to use the convection/microwave WITH the convection feature. If we just use the microwave function, only, we have never had a problem. (Actually, we don't have to turn off the water heater to use the convection/microwave. Winnebago wired the water heater and the convection/microwave to the same breaker throught an ATS. If the microwave is not running, the water heater has power. If we start the microwave, the ATS kills power to the water heater automatically. But we still have to turn off the A/C if using the convection feature.)
As far as a separate line to shore power, it would be easier to just run an extension cord out the window to the pedestal to power the blow dryer.