taultunleashed

There are 3 exits in the large room that you appear in. All three will have force fields. Use the force field sploit on the middle door and this will give you access to where the grenadiers are. Simply go up and kill them with ease as they will be targeting people runing around trying to kill the boss.
Usually its better to send in a ranged to do this as they can kite krixx from the second floor.

Soon as the boss is killed the force field is lifted and you can go back with the group.