Let me ask you a direct question, and I hope you'll respond directly.
Lets say all of those "transfusion alternatives" demonstrably fail, and someone has two choices left: Transfuse or Die; you might phrase that as "Transfuse or Pray", but either way...
...What then? When all other options are exhausted, the prayers aren't working, and your last chance to live involves transfusions, are they permissible?
They aren't. That's where a strong future hope comes in, and the desire to follow God's laws over all else.
That doesn't make it easy, but if one truly believes something, shouldn't they be be willing to make sacrifices for it? People don't think twice about giving their life for their country, so why would somebody be any less convicted?
A country is a real thing. What if someone truly believed in Santa Claus and was ready to sacrifice their life believing that will save Santa/follow his teachings? Would you think that's ridiculous?
Now replace Santa with God, this is what atheists believe...
Lets say all of those "transfusion alternatives" demonstrably fail, and someone has two choices left: Transfuse or Die; you might phrase that as "Transfuse or Pray", but either way...
...What then? When all other options are exhausted, the prayers aren't working, and your last chance to live involves transfusions, are they permissible?