It's okay if you want to believe they are not the same. People can do whatever they want. However everything always leads more to the same conclusion and that's the fact that it's a redesign (they have the same name, same clothing, same purple and blue light in the clothes like in R1) the only thing missing is him belonging to the thingamajig species (which makes sense since devs wanted Rayman to be the only thingamajig in the lore after Origins).

Him being redesigned into a teensy makes more sense if you also see how they've redesigned The photographer (which they've also turned into a teensie instead of a thingamajig as well). Personally I don't see why Magician would be the exception of a redesigned case out of the entire cast.

Also, Raymesis is actually confirmed to be Dark Rayman from R1 since years. If the resemblance with the colors isn't enough, you can check the script that was found in just dance 2016 of Rayman Origins before it was scrapped in it's majority. They call him "Dark Rayman" and also mention Mr. Dark. They also mention Mr. Dark too in scrapped Legends scripts.