So I don't play here very much anymore but I'm doing quests and I don't think it's using my 30% discount card? I have a 10% buff but I'd rather us mine... have things changed?

The random buff combines itself to your 30% card.

I can verify the 30% card is working, I've got mine locked in Inventory and just did some quests where I bought from Restocking Shops. It has always worked for me since I got it and the only times I've seen it not work is when the user didn't have it in Inventory for some reason.