How are you going to control whether you want it to Purge or Purify/Cleanse Spirt? Your current Help/Harm macro works because the it can only be one of the conditions at a time but if you’re using @arena1 and @party1 both will exist at all times so you’ll need something else to pick which one to do.
On the other hand, if you want to just set this up with @focus and tweak the conditions so it does one thing for a friendly focus and another for a hostile one then you can reuse some of the logic you posted.
#showtooltip
/cast [spec:3,@focus,help,nodead] Purify Spirit; [@focus,help,nodead] Cleanse Spirit; [@focus,harm,nodead] [harm] Purge; [spec:3] Purify Spirit; Cleanse Spirit