Hall was moved for both salary reasons and the fact he was capable of freeing up a player like Larsson. He was a significant asset used to address a more significant need on the roster, stabilizing the defense. There was no UFA signing out there capable of doing that. Those types of players simply never become available.
Eberle on the other hand didn't hold near the same value, so yes, his salary was divvied up to fill depth on the roster. Strome fills a depth scoring need.
Ultimately, the defense was always a more glaring need than our wing depth. Although we're seeing that be an issue now, it will always be easier to address.
Yes defense is harder to aquire and so you must make the most and that means trading a Taylor Hall.