ok, there are a few issues. first, you want to put the mod-sequence (chain heal in that case) before the other one, unless you want to write nomod in every bracket - yours won't ever cast chain heal, right
?
then, how do you want it to behave concerning your focus? yours, logically, will not use focus targets unless you neither have a mouseover nor a regular target, is that intended?
[@target] is obsolete, that's what it does unless you specify another target - you can save characters here.
lastly, showtooltip without conditionals will always show the right one that is about to be triggered in the current situation.
Code:
#showtooltip
/cast [mod,@mouseover,help,nodead][mod,help,nodead][mod,@focus,help,nodead][mod,@player]Chain Heal;[@mouseover,help,nodead][help,nodead][@focus,help,nodead][@player]Earth Shield
edit: also, [help] and the similar conditions incorporate [exists] already. There have been some glitches about it, but all in all it works.