These Cichlids not being known for being a very social animal in general is definitely a good point. However, if danger is in the tank, a couple more barbs would stand way more of a chance than just two. The idea is to give the barbs a chance by taking turns getting chased rather than the two getting harassed all the time. Not saying its a good combo, but it may help things work out here. Setting up three separate groupings of ornaments may help too. One in the middle up front, two in the back corners or such. Hopefully you can get the three fish to stick to their own houses.
Note: By ornament groupings I mean three groups of plants, a cave for the fish, etc. with noticeable gaps in between the three territories.
When you set up your ornaments, post a picture of your aquarium.