Beginner question…as a lvl 11

I find the person I’m playing with will tend to get a lot of the exact mythic they are going for…whereas I feel that I need to get lucky and summon just the right thing to get mine.

For example, I have been going after Batman icon and some games i can’t get a tiger until wave 50-60. Am I doing something wrong? What is the strategy to maximize getting the mystic that you want?