Fortunately, Tekkub is on it. He's compiling a spreadsheet with quest XP changes over at Google Docs, and he needs your help to collect more data. If you want to help, you'll need a character on the PTR in the affected level range (30–60), and you'll need to go do some quests and note down how much XP you get from them. Then just email Tekkub (his email address is on the spreadsheet) with your data, and the collective information base of the WoW population will be increased! Ah, science. Personally I'm not seeing much of a pattern on the spreadsheet yet, but I'm sure there is one, and we will figure it eventually.