We can see Coalescence crafted then demonstrated here, both alone and with the other trinkets: https://www.twitch.tv/videos/437561307?t=08h31m50s
Honestly I don't think anything could've been more disappointing. People complain about or praise legendaries when they come out all the time, and every one has people that have really enjoyed it. These trinkets are different in that they can't appeal to different people. They have exactly the same effects, and just build on the same aura as you get more of them. Every other legendary in the game is fiercely unique. Whether people like it or not, it's different. There's no options here. There's just these bubbles that you can slightly change the color and texture of with more trinkets. Even if we're going to have this aura with all of them combined, they could at least have different parts of its effects with each individual piece (i.e. the black orb with Coalescence, the original aura with Aurora, and some purple bubbles with Vision). Legendaries are legendary because there's nothing else like them. These feel like we should be getting the three existing trinkets then the next ring and throw all of them into the mystic forge to create the actual legendary; they're not legendary in their own right.