I've had some luck with two mages in the party, both of whom are equipped with the appropriate staff. Set both of them on the barrier (Energy Barrage is your friend). Meanwhile, click the "Attack my target" button and the rest of the party will attack the barrier along with the mage. It seems that only a mage may target the barrier initially, but once it's under attack, anybody in the party can damage it. At least that was my experience with it.
Also, make sure that both mages have Dispel. That will help with the barrier's barrier.
I had Solas attacking the barrier around the second body pit at the Citadel in the Exalted Plains for a solid 10 minutes before I thought to click "Attack my target." I literally went down to the kitchen, made a peanut butter sandwich, and came back and the barrier still wasn't down. Of course, by that point, Solas was out of lyrium potions, so the revenant cleaned his clock (or polished his egg?), but that's a story for another day.