Raid Boss card drop chance

I find that when i battle lvl 70 raid bosses and die say 2 to three times and use revive i almost always get the bonus card. I can kill lvl 70 fire card without dying but after 10+ kills i still havent got one bonus red card whilst i got water and light raid boss cards very easily. You're prob going to say revives dont improve drop rate and that i was lucky, just curious about other players experiences.