The only game you need the BCA fix for at the moment is New Super Mario Brothers.No you dont need an sd card.I have burnt over one hundred disks using -dvdr RITEK dye with Imgburn at 4x using Samsung or Pioneer writers and never ever had a coaster.
I dont think its the wasabi at fault its either
1.the isos are faulty
2.the brand of dvd disks you are using
3.the dvd burner
4.maybe faulty or misaligned laser on wii drive
Try some -r disks with Ritek G5 dye (ask the shop)
That was directed at Tybriah