Ok, so it took like 3 tries for everyone in the pug group to get on the same page, but we did eventually complete. Here is what I learned.
When you first get into the raid zone, you are on a platform overlooking the battle area. We then activate the raid (I did not do this but I think it is a switch) and a ddoor opens up behind us on the platform. Enter ddoor to start raid.
There are a few things to be mindful of:
1) the puzzles (on the walls around the square-ish battle area) need to be kept "unsolved". There will be constructs that spawn that will attempt to complete puzzles every so often. They are normal trash mobs and easy to kill. Best method was to call out "constructs" and we dealt with them quickly. If the puzzle is solved or close to it, you can go over and move tiles to unsolved it. This constitutes the raid fail timer. If all puzzles are completed, you fail.
2) there are 4 red named (bosses from Sharn quests) that will need to be dealt with. Easiest way is to choose one at a time. They all have a massive attack that can be saved against, but can instakill you if you fail. Not sure what the saves are, but I died a few times as a result. The trick with dealing with these bosses is that they need to be dps'd down and then have the cannon moved over them for a titan-like kill shot. This was the most difficult part. Coordinating where to kill and having the gun ready and in the right spot. It can't be close, it has to be exactly in the right spot to work... and it has to be a few seconds from when you dps'd down the boss. So, you have like only a few seconds to fire.
3) Once a boss dies, 2-3 folks will get an aura (circle) around them on the ground that matches their element. I believe they were red, blue, green and purple... There are 4 runes on the ground in each side of the battle area that have matching colored circles. When a boss dies, it will give 2-3 random players the aura. You need to then run into the rune with the corresponding color and be teleported to an area to fight the appropriate elemental. (I never had the aura so I don't know exactly how that fight goes.
You have to do this once for each boss (so 4 times). Tow are fairly easy and can be kept relatively still. Two move quite a bit. Irk travels around on one of those floating sky sleds in Just Business and another caster type will teleport. These two took the longest to kill. Eventually, there will be other regular trash mob devils that spawn, but are easily dealt with as well... but I think that doesn't start until after two bosses and elementals are dead.
Once you have killed all the bosses and their elemental, the final battle begins. All 4 bosses come back as well as the fallen angel in the middle (who is the one who resurrects all the bosses if you fail your cannon shots). This was a bit confusing on how we completed, but I believe you have to take down all 4 and the end boss in a timed manner or else they will respawn. Not 100% certain on that part, but seemed to be the way. Kill 4 red named bosses first, then kill main boss. Timed so they need to be prepped etc...
Overall, not a huge challenge beyond the coordination. Very much feels like Titan, only on a bigger scale.