We are two in a group. Both hit the door about same time to do a boss monster in unicorn way. She ended up ina different boss monster. She ran out and tried to teleport to me. but said I was busy.
Group members should be able to find the same boss monsters or what is the point of grouping.
Not all battles can be shared. Many are this way in DragonSpyre, and one happens to be on Unicorn Way. Was it a door that had circles outside with a 10 second countdown? If not, you can't share that battle. You will each get your own instance.
Note that some towers in DragonSpyre, you can enter as a group but nobody can join afterwards. That's just how it goes.