height is somewhat arbitrary. just depends what look you're going for. but, if you go too high, you really need to core out the area behind the text so you don't get sink marks or other distortion happening due to the thicker wall section.
generally for raised text, i go about .020 inches off the surface.
you don't really need to draft it as features that small won't really stick in the tool. plus, it will be shrinking away from the core anyway so you shouldn't really see any drag marks assuming the sides of the text are polished and not textured. but, if you want to put 1/2° draft on the vertical surfaces that won't hurt either. sometimes with text it can be a pain to put draft though.
Thank you very much for your advice. I have it as a 0.5mm high at the moment but wanted to verify that it's ok because it was casting a somewhat prominent shadow in renderings. Good to know that it is in the ballpark.