Thought I’d update my progress. I have 3x 30w Tradfri drivers working with ST now! Thanks to @bschuring for the help!
I looked through the logs and see what you described. The 30w driver repeatedly failed to discover properly. I see the 30w association event come through, but the first or second discovery commands after that always fail. One thing we could try is to change your network channel. You are currently on channel 24 and it has the worst RSSI (-83) of all the channels. There are a few with better RSSI that we can try and see if improves things. If that doesn’t work we could try to reform the network. That would require you to reset and rejoin your devices, but would give us a clean slate for Zigbee. I will start with forcing the channel to change. Try rejoining the device again and let me know how it goes.
This solved the issue for me and hopefully helps someone else out there having heaps of difficulty paring Tradfri devices or other Zigbee devices.