As far as the "washout" you refer to (AKA "rain fade"), that is usually caused by the tech not aligning the dish properly for highest possible signal.
In regards to the DVRs having to use dual coax, that shouldn't change the way the cables are ran around the house.
However, for those of you who are thinking about getting DTV, we now are doing the KA/KU SWM (hi-def...SWM=Single Wire Multiswitch) system. These eliminate the need for the second line requirement for DVRs and HD/DVR receivers. You only have 1 cable coming from the dish to a special splitter, where it splits off to all the other receivers. Each receiver is assigned a "channel" that it uses to communicate with the LNB on the dish, and there are a total of 8 available channels. DVRs use 2 channels...one for each tuner. So you can have up to 4 DVRs on 1 dish, or 8 standard/HD standard receivers on 1 dish.
In order to get this setup though you have to be a new customer and order an HD package. DTV does not do them on HD Upgrades...new installs only.