Gagner on waivers would have been worse for the Oilers than Gagner for Spooner/Strome because of the money involved. The Oilers did not acquire Gagner because they love Gagner, they did it because Spooner was useless (and Strome before him) and needed to take money to move that money.
Strome at 3C generated no offense. Almost legitimately none. At wing in the top-six, as he has been playing in New York, he generates the same mediocre 30 point pace he did on the Island and here last season. The only good argument for keeping him IMO is that his buyout is more favorable than Gagner's.
Of ALL the things to harp on where the Oilers are concerned, Ryan Strome is not on the list IMO. He's a mediocre player that was not part of any solution for the Oilers.