Kyra is a lot better in fewer man groups.
Ultimately each player plays less in a large (4 player +) group. Playing less means you need to heal less.
In 2 and 3 player games she tends to break the game. I can go through the whole game without worry of dying. I can also use her ability often and STILL have enough space to explore most locations fully.
My Ezren/Kyra duo is broken. They never have a challenge.