First thing's first: there is no way to spoil a baby - especially under a year old.
Where is the ratio 5:1???? There is supposed to be no more than 4 babies/toddlers per teacher until TWO YEARS OLD!! Five to one IS to much! No wonder you are overwhelmed!
Letting them CIO is not good for the babies and you are right to feel that way - if you try letting them cry for ten (or even five!) minutes, then YOU ARE NOT DOING YOUR JOB!! If I EVER suspected my son's daycare of this, I would pull him out IMMEDIATELY, demand my money back, and file complaints against the teacher, the director or supervisor, AND the daycare!!
Babies MUST BE COMFORTED!! YOU are their CARE GIVER while the parents are away. You are being TRUSTED by them (parents and babies) to do your best to comfort and soothe them! If you cannot handle that many babies, perhaps you should not be with them. Maybe your work can put you in a room with children that are more independent....perhaps the 4yo room. If you are trying to sooth EIGHT babies, then WTH is the other teacher doing while you are holding one (or two) of the babies???!!!
IF I were the parent of one of these babies, I would be happier if you had two happy babies on your lap than none, or even just one, while letting the others just scream and cry.