Seems to me like something perfectly normal.
Buying the expansion through points is actually a bit less expensive than buying it outright (though it doesn't come with the neat perks)
Your real money spent will be able to purchase the expansion at a later date at a cheaper price.
If you're complaining that in order to get your cheaper price you have to wait longer, well, I've seen many people going to the forums complaining they bought points a week before double or triple bonus points promotions, and I don't pity them any more than I do you.
You bought codes for points. That's what the cards say, that's what they're for. You could have bought prepaid credit cards, but bought points instead.
There are things points cannot buy in DDO. The plethora of permanent gold seal hireling contracts (Elieri, the panthers, owlbears, scarecrows and now guardians), exclusive cosmetics...
Buying expansions before they're released to the f2p public is one of those things points won't buy.
Finally, I SINCERELY doubt that was your first encounter with customer services, or that you've been as mild as you're implying here. They've been nothing but charming to me at any point I've ever had the pleasure to ask.