The issue with Shield Swipe is that while it most certainly ups your DPS, it also has the unfortunate caveat of generating no extra enmity while being on the GCD. What this means is that for the extra damage boost you're sacrificing 2.5 seconds of enmity gain. This may not seem like much of an issue where you are now but in the later battles, the heals become more potent and the dps get much stronger, being able to close the gap between themselves and the tank (you) fairly quickly.
That doesn't mean Shield Swipe is useless though, in long fights (like Titan HM, for example) where you'll pretty much be unloading on the same target for an extended period, you can feel free to toss a few in here and there for the damage boost. In addition, Shield Swipe works as a wonderful way to recoup lost TP during long battles of attrition, due to its wonderfully low cost of 40 TP.
Basically, it's a good move that every PLD should keep in mind for the situations in which it shines, but don't get too crazy with it.