As far as I know, if it is verified by VISA, there is no need to show the card at check-in. I have purchased tickets online at cx.com on SIN-HKG-SIN route and transaction was done under verified by VISA mode. At check-in, there was no request from the agent to show the card for verification.
If you wish to have a peace of mind, suggest you call the e-Services Centre to check with them:
Worldwide toll free:
+800 2747 2200
Also, from what I know, if there is a need to verify the card, once it is sighted on the first sector, there is no need to be sighted for subsequent sectors.