Hmm... I WT A LOT (I did, at least, I took an about 6 months Pokébreak :P )
I did got a lot of shinies, releasing the hacked one (starters "meet" at level one, some obious things like this), so I don't get myself or anybody in trouble. I do have a level 100, 6 Iv shiny Medicham, with loads of ribbons and maxed contes stats who make me doubt a lot, but then, hatched in an egg in Illumis... Meh.
Never got a legend, though :3
I also get lots of breeding materials, some 5IVs, cute balls, and even a Jap event Magikarp :3
I was just asking myself, since I took a 6 months break : are Wonder Trade Wednesdays still a thing ?
And, by grace, release the junk you receive, do not send them back @.@ The most frustrating things are receiving level 2 Zig/Pooch/etc in ULTRA BALL. Like, the guy/girl is super advanced in the game but go back in the beginning to WT junk ._.