I think you've answered your own question.

Date of issue = when your Asiamiles are deducted, tax deducted from your credit card, and the ticket becomes "usable", and the e-ticket is issued.

If you look at the "Manage My Bookings" section online, it tells you if your ticket hasn't been issued yet. If it's already issued, you'll be able to download a copy of the e-ticket (in PDF format).

Hope this helps.