Winnipeg average about a goal per game more than Nashville, yes. And? Poile should have allowed one of his top four defensemen to walk in some effort to shore up the forwards, a move you don't even know existed? Smart play.
Not only is Ellis integral to the Predators total team offense, an offense that is driven from the back-end more so than almost every other team in the league, but last season he scored at a .73ppg pace (the same as Seth Jones and Drew Doughty; slightly higher than Subban, Josi, Yandle, Pietrangelo, Rielly, etc.). He played half of a season and was still in the top 50 in defenseman scoring. The next closest player in terms of games played to make it into the top 50 defensemen in scoring was Spurgeon who played 17 more games and scored 5 more points.
You're really prepared to make the assumption that not only could a deal have been made that would have traded Ellis for a forward, but that such a forward would score enough not only to completely negate the absence of Ellis but to make the team better despite his absence?
Bold strategy.