Questions about Lich

New player that's been getting back into the game and I had some questions about Lich. My group has been trying out the boss but we've had repeated deaths to the homing orb, it appears to go through walls and will even leave the bossroom if people remain in the room to keep the fight going. Is this a known/common issue or is it possible we're just doing something wrong? We haven't tried running them into the minions because I was bringing Holy Purification to clear them asap.

Also is cleanse still supposed to remove the purple/blue curses? I haven't been able to pull it off but I'm not sure if it needs to be done very quickly and I'm just too slow to cast cleanse.

Thanks!