Blinker Trouble

Try changing the blinker fluid. The viscosity breaks down over time and causes all kinds of issues.

Or check your grounds and make sure no bulbs are bad.
"normal" flash rate is about the same as any new car is. There might be a standard they have to follow on that. However, grounds can affect the blink rate and some flashers can make them flash fast or slower than normal. The HD flashers are made for when your using a trailer. They consider the extra load the other lights put on the system.