it relies on you having a reliable way to root/stun/snare your target and knowing who to kill first to avoid being AoE'ed to death. it also requires low latency - sub 100 is preferred if not necessary. 5 ret pallies can man handle most AV's with good healing macros... unless they run into a 5 boxing shaman. assuming you can repeatedly prevent the motion of your intended target then you end up with the same synergy that a 5 caster group gets in terms of focused fire plus generally more tankability and simply more exciting gameplay.

you also need to have an addon intelligently re-following, simply spamming it multiple times per second can cause problems and having it as part of your spam key can cause you some arthritis