I noticed last night that if i just chain heal my party when standing next to elementals it DOES NOT jump to the pets. I'd need to test it, but I imagine this means that a chain heal on an elemental will also not jump to other elementals.

I use my "Beaten" macro for boss fights where I'm using earth elementals. It just heals whoever the mob is whacking:

#showtooltip
/cast [target=focustargettarget,help,nodead,exists] Healing Wave(Rank 7); [target=target,help,nodead,exists] Healing Wave(Rank 7); [target=player] Healing Wave(Rank 7)
/assist focus

I tend to just let fire ones die if they get aggro.