From what I’ve seen there are 2 types of game artist. The first does all the crazy stuff that makes you think, wow I wish I could draw like that. And the second is an artist that does representative sketches to show ideas.
Now I reckon you’d have to be in a pretty big company for them to afford to have someone doing one of those jobs exclusively, but what I’m trying to say is that as long as you can represent your ideas clearly, the apparent quality of your drawings won’t matter.
For a good example see if you can get a copy of the making of the royal tenebaums, the director uses simple representative sketches very well there.