The Redskins avoid that by taking a significant dead money hit every year. They don't put off the inevitable and then get hit with a huge one-time dead money hit when they blow up the team. They blow up the team a little bit every year, on an on-going basis.
The Skins are only looking at the cap numbers for a player's first two years and the resulting dead money number. They already know that every player they sign this year will be cut within three years.
They are locked into this cycle, because they don't have the cap room to keep any of these free agents past three years when the salaries start escalating. They have to cut them, whether they want to or not and move on to the next guy. My guess is that their cap spreadsheet already shows the year that Randle El and Archuleta will be released for cap purposes. Basically, they are just renting all these players with no thought of building long-term continuity.
Oh...and the CBA extension gave them a get out of jail free card. The Redskins approach only works as long as the cap number is rapidly escalating. It's kind of like the Donald Trump approach to highly leveraged real estate development. More and more debt. As long as the economy grows at a rate fast enough to cover the debt load, it works.