When Astral Heron is played with Here to Help , does Astral Heron apply his ability to his own cost when played as the Second card

No. Astral Heron's trigger only fires on your first card each turn, and it discounts the next card you play — never the card that triggered it.

Here, Here to Help is the first card (and Heron was in hand, not at a battlefield, so the "if I'm at a battlefield" condition fails at that moment anyway). Heron then enters as the second card, so nothing fires for him — and even in the case where Heron is played as the first card, he discounts the card played after his ability resolves, not himself (FAQ #12236, #11762).

The one thing Here to Help does for you is reduce Heron's own cost by [3] as it plays him from hand — that's Here to Help's effect, not Heron's. Note the trigger condition "if I'm at a battlefield" is checked when your first card is played, not after (Rule 383.2.a.1), which is why the timing here matters.