Garlick's value is having options, he won't be here long, but yes obviously a RH power bat complements Bruce. Whereas Williams just isn't needed on this lefty-heavy team.
Gosselin's ability to play SS/CF and his success as a PH last year may help him hang on, but probably he's gone during one of the roster reductions too (but would hopefully clear waivers). Seeing him as a DH really is a surprise. Yeah, he's hot, and of course it's silly to say this after just 10 innings of baseball, but it seems like Girardi is taking an overly relaxed approach to this short season in terms. With every game counting 2.7 the smallest decisions about line-up or relief pitcher are magnified.
I've also seen it said that with the new format the top 5 or 10 teams can be a bit more laid-back, since seeding isn't going to as big an advantage. But the Phillies are not one of those teams.