I'm not GGL these days, but my recent calls to You First (so same team) confirms that I have also noticed much longer wait times. Same for email. Responses used to be speedy, now 2-3 days turnaround is at the quicker end of the scale.
I think this is just another example of BA's general attitude to customer service these days. BA management simply sees it as a cost and inconvenience. If reducing service levels annoys some of their most loyal customers, so be it. They think people will just keep paying them money, no matter how bad the service gets. Which in some cases is true, due to BA's dominance on some routes, but even then there is only so far you can stretch an elastic band before it snaps!