My experience is that Gigantix are just generally bugged. I experienced the 90 sec despawn, then a few minutes later was two shot by one when it wasn't even raining, much less storming.
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I used to think BP was annoying when I was locked out of UQs and zones. Now I'm glad it exists for the reasons @Anarchy-Marine stated. Think about it this way, doing the grind now means you'll be ready for new/higher rank UQs and the event starting on the 23rd.
The thing is, this gear will barely cut it by Christmas. The roadmap is up and relatively detailed. I laugh all the way to the bank when someone buys a 4*out of my shop. Unless they've got ono with a Fixa and are buying mine to multiweapon, it is mostly a waste.
@Scarface1 Probably best to find friends/alliance members to help you. That way you can just spam triggers until it drops. You need the large number of kills and PSE Bursts that a full MPA brings with it to help the RDR boosts get the drop you need.