I don't want to sound a pre-emptive victory, but that sounds like people who were unfairly attacked a lot suddenly not being attacked until their ratio catches up, or vice versa (which yes, is exactly
what Jofer theorized in the week 10 PVP thread).
Basically, the system is trying to enforce an even attack:defense ratio now with logic that makes sense to do that (as opposed to before where it was encouraging attacks against people who've already been attacked a lot), so it's expected to see weirdness until everyone's ratios start evening out.