I got my first hundo on squirtle CD. A wild magmar during the event.
Then I hatched a hundo Magby only a few minutes later.
Then I got a (not shiny) sunglasses squirtle hundo from the research.
None at all, then 3 in one day.
Although I'm still yet to raid or trade, a single hundo. And only hatched the one, which isn't meta relevant. Pretty disappointed in that. My raid luck is a mix of insanely good and bad. I got two 98 zapdos, one 98 moltres, and two 98 gengar on their respective raid days. However I've never gotten a hundo, didn't get any shiny Articuno/zapdos/gengar (one moltres), highest Mewtwo was a 96 and most were really bad, in total have actually had less 96s/93s/91s than 98s (enough so that while my 98 count is miles ahead of expectation, my 90+ count is miles behind expectation), and finally of my six 98s from raids, five had 14 attack.
Obviously my sample is pretty small (200 raids) so I'm not even at expectation for my first hundo (and six 98s versus expectation of 3), so at the end of the day it's really random.