I haven't seen the starting price change after the auction has begun, so that might be an indication of really low participation. My general strategy is to bid second from the bottom but in your case I'd look at the loads for the flights and then adjust accordingly.
I've got a $450 bid in for MIA-MAD on a flight in January that has steadily been doing down in availability. It's been stalled at J4 D2 for a couple of weeks now, I'm crossing my fingers.