It makes sense. When Howard is in net for game 7 of the second round wouldn't you want to maximize the teams talent on the ice (a good defensemen), rather than having that talent sit on the bench (Gus). He's played great and that's why I think it would be a good idea if we could get something for him. I remember for a little while people thought he was the answer for Toronto when they had Reimer and Gus. Now if Howard were to get injured in the playoffs it'd look bad, but it's also a matter of if your willing to take the risk to utilize the potential elsewhere on the ice. More often than not teams don't have to use their backup at all in the playoffs.
And then there are other times when teams ride their backup to the Stanley Cup, ala Osgood in 2008.
I get what you're saying and it's a valid thought, but right now we might have been well out of playoff contention if not for Gus' ability to step in when Jimmy needed him to. He is actively demonstrating value to this team and keeping us competitive in the standings, and I think it would be quite risky to trade that type of insurance away.