Appreciate the effort, a few things;
Your damage should be considering the Blood offerings bonus not the total damage; so 8% for sun disc EX rather then 24.
The 10% self damage is significant, in MK9 these buffs were in fact entirely avoided because the self damage was considered worse then any gain, a simple way to do this is subtraction, so three ex sun dics -10% makes for 14% Benefit.
Then there is blocking. When it comes to knowing the match-ups Kotal Kahn is pretty damn easy to block, and avoiding obvious parrys (and it's set-ups) will be a big deal. Realistically I would probably average the damage between blocking and hitting, which is still giving the dmg a big beneifit as it's assuming you don't do any low dmg hits. So we are getting something closer to 16% total bonus damage at -10% self dmg for a 6% advantage, similar to what you would get for the throw. If you ever do anything lighter you rapidly loose out and start getting into negative damage.
But wait there's more, by using the blood you are loosing out on a lot of oki pressure. While you can parry set-up and hope they fall for it, you otherwise loose out on the ability to directly pressure them, which is one of the big advantages of a knocdown. This is especially bad for Blood God which is lacking in offense to begin with.
All this combined means that Blood offering can be good but it will be inconsistent, which is why the guaranteed dmg and oki tend to just be better.