Something that seems to have went under the radar with all the leveling stuff and Argus invasions the past few days, is the fact that you can repeat already completed invasions and gain it's reward.
How does this work?
You either take note of when one of the 3 invasion is going to expire or simply don't do them at all until they're about to expire, whatever you find the easiest really. Enter the invasion short before it's going to expire. Once it has expired you won't get kicked out, but will be able to complete over and over by joining other groups people made shortly before the invasion was set to expire.
On avg you can do this 2-10 times depending on luck per invasion that is about to expire. Invasions expire every 2 hours, which means around ~26 invasions per day, all of them you can repeat 2-10 times (Avg is around 4-5) netting you up to 100 invasions completed PER DAY if you do them all. This can boost your legendary chance massively together with all the gear tokens etc you'll obtain.