The rankings are shown to the player, and the grade the characters are, and showing the health the characters have, giving you and idea what the battle will be like. Unless you don't memorize the teams members you have.
On the bottom of the screen, the possible drops are show, the more powerful the characters the high the rewards.
The combiners have two characters, the combiner. Also it will show the valuable rewards of cores and other curency that will make the very, very, high risk worth it. The combiners have extremely high high health, and you should know that. But the other smaller ones can have pretty high heath too, or lower, depends.