Not sure if this suggestion have been brought up before, or will be fiercely contested by other forum members, but here goes.
At the moment, Arena's only stat that matters is Initiative (though we all know there's a 10% element of other stats as well). This initiative is based on the overall initiative of the entire team, and is divided equally to all 4 characters. So its safe to say, the team that takes the field in term of passive barrier, will also be the player that have their characters either do standard attacks or mysteries first in terms of their position (i.e. Passive Barrier team will position 1 will always be faster than No Barrier team position one, and this applies all the way to position 4).
So in this method of Initiative being applied, its pretty much a huge handicap to the No Barrier team. Losing on barrier as well as initiative on ALL 4 characters in play.
Keeping in mind that Initiative is still necessary, the suggestion I have in mind is still keeping the Passive barrier based on the overall initiative of the team. But for individual characters, these initiative should still be based on their inidividual Initiative. So basically same to outside Arena PvP play. This way, it isn't automatically known to the player from the start, before the 1st attack goes in, that Passive Team will have ALL 4 characters doing everything first to their opposite respective counterparts.
Its still possible that the Passive barrier team will still have all 4 characters going first, but it won't be always the case. As we know some players have all their initiative heavily placed on their 1st/2nd Position character, and have terrible initiative for the rest. This suggestion, in my own opinion (and everyone else who would like to chip in to contest, have their opinion as well which will all be duly respected), would make the gameplay slightly, if any, more balanced.