While I'm not directly involved with the weekly guild summit that @Eej
holds, my guild is and we have some input into the discussion topics and the chance to provide feedback. While I'm sure DB has excellent data on just how many players have been leaving and how many new players they've been attracting, what they probably don't have good data on is how many people are on the fence and close to leaving.
I don't have exact numbers, but my family of guilds has lost somewhere between 20-40 players since the introduction of the pvp changes. Sure, some are taking a break and might be back and some might have just moved to other guilds, but that level of attrition is staggering. From what I can tell from various line chats and the forums, player mood isn't improving and many guilds are struggling to recruit.
From my perspective, the introduction of the pvp changes was the Titanic hitting the iceberg and everything DB has done since then is just rearranging the deck chairs.