Thing is, from the premiere of season 3 I was actually expecting some heavy stuff. The more I've seen of the season so far though, the more I realise that premiere was actually written as part of series 2 and pushed back for whatever reason. I can't remember where I saw it, or why they did it but the episode revolving around The Purge was a last minute addition which allowed Rick's prison break to kick off the next season. If you compare the first and second episodes, I think you can tell.
I still have high hopes for the rest of series 3. It hasn't been bad at all in the slightest, but I'd need the next four (or however many there are left) to be great for it to sit on par with series 2. I suppose we'll have to wait until Sunday and see.