I do enjoy Barrage-type teams, and they can even get past the whole shield negation problem with some debuffing. While not top-tier, these types of teams can open up a lot of different strats to cause headaches. One of my fave examples of this type of team is:
I am going to admit, I copied this team from a person that I used to run into a lot when I first started battling. While susceptible to shields, it can devastate teams without them. It has a good mix of delayed and direct dmg (undead and humanoid), as well a DoT healing with Plagued Blood. It is teams like this that really tap into the strategic aspect of pet battles, and I wish these type of teams were a bit more viable than they currently are. In order to protect against shields, you could swap out the marionette with a debuffer, such as Foreboding Flame, Chi-Chi, or Voodoo Figurine (among numerous others). You can also trade something for a Clockwork Gnome, Lil' Bling, or my favorite DoT pet, the Fel Flame. This sort of team will do well, even if the opponent has a shield, though high-health shielders will give it fits. Still, nice to have options.