Yes, it looks as if you have implemented the RS0012 sequence from page 31 of the RS0012 datasheet.
However the sequence from page 21 of the RS0010 datasheet checks the BUSY flag.
So I would be inclined to add a _delay_ms(2) for each command. Well certainly the Function_Set and Display_On_Off commands.
Or why not check the BUSY flag yourself ?
No, I don't have a WS0012 display. If you are in the USA you could send a display to Bill Perry. (PM him first)
David.