You misunderstood what i said bro.
1. Around 9,000 per Turn is damage you receive from World Boss in one Turn (=sum of all girls base damage) at fight 23 - this is when you dont allow World Boss to make 3 gem combination for damage increase. So your own HP is 20,000 then you will loose fight on turn 3 in front of boss and vice versa, if HP is 54,001 you have to defeat Boss on Turn 7 provided you have denied major damage boost to Boss.
2. Sheela na gig damage was way beyond it is now. (Multiply 99 to to damage it is doing now). So Basically you cannot depend on on Sheela alone.
I am having suspect that Developer planned it this way so that on First World Boss Event - you can reach Fight 5 to get 5 libido crystals (Not Fight 10 because of scaling HP). Now you have added incentive to get Mythic girls from Colosseum event (extra reward at 10,000 points). Now on second or subsequent World Boss event, you can reach fight 10 with upgraded ability from your previous efforts to get more crystals. Then again loop of getting crystals - upgrade ability of a new girl - do more damage to World and rise on a step ladder fashion. BUT, Sheela damage bonus was unintended - seems to have broken this logic therefore it was debuffed.
Just enjoy the game and focus on getting Mythic/libido crystals during future events - you will witness high HP World boss to be weak against your deck.