I had debated engineering some guardian weapons for better AX performance. However, last time I did that - some time back now - I picked the Guardian Plasma Chargers as I'd seen videos of them working really well vs. Interceptors - particularly the Orthrus. Upon unlocking and installing them however, they did precisely ZERO damage to anything I shot them with. I landed solid hits, all charged up. They. Didn't. Work. At all! Wasted two BP unlocking two sizes of those! I'm hesitant to unlock the Shards as I was worried they'd be equally broken. Plus, while I've acquired full loads of many Thargoid materials, I suspect I'm missing the specific ones needed to Engineer the anti-anti-Guardian field thing. Those materials are exclusive to LIVE Titans, right? I don't think I managed to collect any of those.
I saw someone last night in an Anaconda firing a giant huge white blob at at Interceptor, doing massive damage to Hearts each time. Dunno what that weapon was. That "blob" might have been lots of smaller shots (Shard?) but it was very glowy so just looked like a giant blob from a distance.
Currently using regular AX MC's myself, useful for keeping the Scout off the heavy damage-dealers while they engage the Interceptors, but a bit slow when dealing with said Interceptors myself.
Like I said, I've got full bins of loads of different Thargoid-related materials, but none of them seem to be the ones I actually need! I didn't even have the stuff needed to unlock the other AX weapons - you know, those "loads of materials each" unlocks. Sigh.