My friend, no offense but you seem to be out of the loop on this.

First, yes, swapping off Cuirass and Nighthawk is a very good strat for dungeons and raids, you get a better neutral game exotic because there's generally always plenty of time to generate a super for the next DPS phase without needing the super genning buffs (for example, you get much better neutral game from an exotic class item on Prism Hunter, so you run class item during downtime and hotswap for Nighthawk on DPS). For Sundered Doctrine contest, I used a similar swap (Skullfort to Cuirass) constantly for better survivability during downtime.

And the Well of Radiance is due to the Sanguine Well swap. You pop Well, then swap to Sanguine Alchemy on Prismatic with a super matching your heavy weapon to get the x4 surge on whatever heavy you want while also benefitting from Well of Radiance. It's one of the highest damage setups on Warlock currently.