Hi ruffriders23, I assure you that nothing about the raid boss drop rates is different from the mobile server. It's the same drop rate for raid boss stages of the same level. If you got boss cards within several tries on mobile by killing the level 45 raid bosses, you were lucky. It doesn't necessarily mean that you will get one boss card within the same tries every time. Besides, there are more active people on mobile server, which means you have more active friends and guildmates who had help you with the raid boss and you had more raid bosses that you could choose to fight, therefore you got more card rewards from the raid bosses.
Hi thievingsquirrel, thanks for your feedback. The boss card drop rates in low level raid boss stages are low, but those in the high level raid boss stages aren't low. In level 70 stage, the drop rate is 16%. That doesn't sound low at all.