I think the main thing with the Batarians is that their eyes were just black pits. A batarian can't look askance at you, for instance, because he always just seems to be looking in the same direction. Look how expressive Legion was able to be just by moving those panels around his eye; that's a big part of character design IMO, and the Batarians were lacking in that department.
For sure, it makes it hard to gauge their facial expressions and relate to them.
Although, I think that might not be a bad thing when it comes to Batarians. It makes them seem more alien (and, ahem, alienating), and that seems to be what they were going for.
That figure above comes across as both eerie and beautiful to me. Exactly what I want from an alien design. If they had a look that was a little less like two heads were just shoved one on top of the other, it could be more of an design advantage than a drawback.
You know, come to think of it, we never did see a female batarian ...at least, I don't think we did 
Never in a main game. There was one in one of the books, but only for one brief conversation.
I quite like the original Batarian design

That looks like Sid the sloth's angrier older brother.