I think that the number of items you can buy in the platinum store is kind of limited. There's not much diversity. The selection of items you can purchase should be greater. Maybe items that are more exclusive and that can only be obtained with Platinum. Weapons and Armor with good stats. More Vanity Sets, Pets and ETC.
I've been playing MMORPG's for years and that's how most games generate revenue and having a lot of diversity in the cash shop is how you get players to purchase and contribute to the game. I've done offers which is how I get my platinum. But I also don't mind paying 2 bucks for some. Just cause I like the game.
Anyways those are my 2 cents and hopefully we can get more items in the Platinum store in the near future.