MacOS – Why do the Macbook Pro’s WiFi speeds drop significantly when paired with Bluetooth devices

NOTE: This question is NOT a duplicate of Bluetooth and Wifi interfering with one another since Yosemite. That answer pertains to 1) The 2.4 GHz band only and 2) Yosemite only.

Background:

Though currently I’m running Yosemite (10.10.3), I have consistently experienced this issue since purchasing my Macbook Pro (Late 2013, originally running Mavericks). Whether it be a bluetooth mouse, headphones, or even iPhone, whenever I pair a device with my Macbook Pro, my Wifi speeds (running on 5 GHz band) drop by at least %50. I can reproduce this issue repeatedly. It only occurs when a device is paired via bluetooth to the machine. It does not occur when bluetooth is simply enabled on my computer.

At this point, I just don't connect devices via bluetooth anymore since the WiFi drop is noticeable. I am using a Logitech nano receiver mouse (and using up one of my precious two :( USB ports in the process) rather than using a Bluetooth mouse.

Machine Specs:

Model Name: MacBook Pro (Retina, 15-inch, Late 2013)
Model Identifier:   MacBookPro 11,3
Processor: 2.6 GHz Intel Core i7
Memory: 16 GB 1600 MHz DDR3
System Version: OS X 10.10.3 (14D136)
Kernel Version: Darwin 14.3.0

Speed Tests¹:

WiFi speeds with Bluetooth-enabled, no devices paired:

WiFi speeds with Bluetooth-enabled, any device paired:

Troubleshooting:

I’ve ruled out my LAN set-up:

• I use a TP-LINK Archer C8 Router connected to a modem provided by my ISP (running in bridge mode). I use the 5 GHz band exclusively. To rule out any band interference, I’ve tested the WiFi speed on the 2.4 GHz band as well. The same drop occurs regardless of the band.

• I’ve used my ISP’s modem as a Gateway to directly connect to the internet (to rule out the TC-Link Router as the cause). Same result.

I’ve isolated the issue to that of a Wireless one.

There is no speed drop when my machine uses a wired connection (Thunderbolt Ethernet adapter > Ethernet Cable > WAN)

I’ve ruled out a specific Bluetooth device as the cause:

Originally, I thought the issue was with my Logitech M557 mouse. I tested my Magic Mouse instead. Both yielded the same drop in Wifi speed. The same has gone for any device that I paired with my MBP – Apple brand or not. Sidenote: I’ve unpaired the devices after testing. I only have one device paired (though not actively connected).

I’ve ruled out third party software:

The issue persists without any third party kernel extensions loaded. Additionally, with no other third party software running (Dropbox, for example).

I’ve ruled out a specific OS X:

This issue has occurred since purchase, in Dec 2013. Across OS X Mavericks – Yosemite. Additionally, the machine has had a clean install of OS X from a fresh Yosemite image.

I’ve ruled out my Macbook Pro’s hardware:

I ran the Apple Diagnostic Test, repeated times, with no error codes. On a separate issue (blown out builtin speaker recently), I had brought my machine into Apple. I had them run their in-house diagnostic test to confirm no BT related hardware issues. Additionally, as stated, this issue has been a problem from Day 1.

My Question:

Why does my Macbook Pro's WiFi speed drop by 50+% when paired with any Bluetooth device? Is there a solution?

¹Courtesy of speedof.me

UPDATE:

Screenshot of detailed Wifi connection with a BT mouse paired. The SNR and Tx Rate are good:

In fact, nearly identical without BT device paired: