You need to go harm mouseover, help mouseover, help, harm. Otherwise mouseover won’t have priority in both cases.
[added]
That said, given the spec conditions that’s probably superfluous. Which is why I prefer stance macros for Druids.
[/added]
#showtooltip
/cast [spec:1,talent:6/3,@mouseover,harm,nodead]Stellar Flare;[spec:4,@mouseover,help,nodead][spec:4,help]Wild Growth;[spec:1,talent:6/3]Stellar Flare;[spec:2/3]Thrash
Haven’t checked character limits, drop a ,nodead or two if it’s over.