Minor update:
1) Assist mode should work correctly now (thanks Sic!)
2) Added the SpamAssistSpell option to assist mode. Now you can choose to either cast your assist spell once and recast if it wears off (e.g. if just want to debuff), or spam it on cooldown (e.g. if you want to keep aggro).
3) Fixed an INI issue where the macro would spam you with errors the second time it was run.