You have to get them to chase you without stopping to heal back up. They need to think that they can kill you if they just continue to come at you(bro). Don't bring the big guns out until they're gushing blood. Act like a scared wounded animal and then when they drop their guard(or sanc) you drop the hammer on them. It's tricky because every player is going to be different. The more conservative shaman are going to be the toughest because they get to play on their terms most of the time. I'm talking about shaman in general, so this all applies to outtie shaman as well.

A good way to deal with outlander shammies is to gang them with an orc/shaman group. Dispel protective shield and rofl when the orc starts bashing. I know you're asking how does one deal with them solo, but solo is going to be tough plain and simple. A strong ranger would be good, but remember blind;flee can shut down a ranger pretty quickly so keep those cure blindness preps ready.