if i move heron to a battlefield and use emperors divide. does it get the discount still?

Yes — the discount still applies. Heron's "if I'm at a battlefield" is checked the moment Emperor's Divide is played — Heron is at a battlefield then, so the trigger fires and the discount is created. Emperor's Divide resolving afterward and moving Heron back to base doesn't cancel it; the discount is a pending effect that no longer depends on Heron's location (FAQ 11729/11792; Rule 383.2.c).

Note that Emperor's Divide is a spell, so it counts as your "first card" for the trigger. Just make sure it's the first card you play that turn while Heron is at the battlefield — if Heron only gets to the battlefield after your first card, the trigger never fires (FAQ 11906).