You have grasped an important aspect of the game, damages only matter if you can win with that card, so robin would be considered a weak card even with such a huge damage. The best cards are then the ones with high damage and high power, but higher power is more important. However, this is slightly nuanced by the fact that the pussycats clan is all about damage reduction, and if you dont have enough damage, sometimes it becomes hard to win against them, try to find cards with decent power but also decent damage
Here's how the battle works.
You multiply your card's attack(the top number) by how many pills you use. So you have a card with 5 power, and you use 4 pills. 4 x 50 is 20, plus 1 extra, so it's a total of 25 attack.
If your 25 attack beats your opponent's attack, who has, let's say 23 attack, only THEN does your damage mean anything. Damage is what take's away your opponent's life. So that card you used has 6 damage, so now, instead of 12 life, your opponent had 6 life. When your opponent's life gets to 0, you win. You can also win by just having more life at the end of the battle than your opponent.
unfortunately its the random factor or you were playing him and he has less stars or the same amount but went first.
anyway let me break it down
random= you add up both your attack and your opponents attack- e.g 30 atk vs 20atk= 50atk altogether so that means you have a 30/50 chance of winning (60%) and your opponent has a 20/50 chance of winning (40%). if you get double your opponents atk power however (66.6%) you get a garunteed sureshot.
with no random its different. obviously if you have higher atk you win but if you have the same amount then it is the lowest star on the card that wins and if they are the same it is the person who went first.
how do you change this? well there should be an option if you look in the lobby where you accept challenges and that (in red).
anyway to answer your question in the most long winded answer possible, unfortunately damages mean nothing when determining who wins battles wheter it is normal or no random
Damage is the most important fact of the game, lets say your hand is packed with full foward power! Yes, Ottavia/Spiahgi/B Ball/Graff for the Win! Then your opponent hits you with something like Caelus/Tomas/Griezzo, with a single card you have been pushed to the very edge
Higher Damage card are risky, yet is much the most precise way to win, even though power shouldn't be overlooked indeed