Fighting Team bosses, Turquoise Lantern, was most fun and enjoyable thing! They gave a good reason to communicate with players in a world, make friends, create small teams. As an additional reward for all that they gave nice exp. By turning them all to solo or group 10+ fights you removed most fun and nice social part of game. Killing solo mobs is boring. Assembling team of 10+ players in a world is a hard task that rarely happens.
Please, revert this change back! Actually you can make all solo bosses Team, this will make it more fun and mmorpg style game.
If you made that change by listening to screams of individuals who says "I can't kill team boss solo, and I do not want to team and communicate in a mmorpg" then it's clearly a bad decision!