The easiest would be for the shaman to auto follow the druid and assist their focus who is another dps caster.

For the shaman, I'd go with a castsequence... Flame Shock, Lava Burst, LB, LB, LB... until you can Lava Burst... LB spam until you need another Flame Shock, possibly another LB before the Flame Shock so you can immediately Lava Burst after the Flame Shock which makes it a truely looping sequence. It is not optimal, compared to playing the dps solo, but its passable.
Another option would be to use /castrandom with those four spells, but because you want Flame Shock up always and to not cast it while its up, a sequence is probably better.

I agree with previous posters, give the shaman a DPS macro which you spam.