I thought bats are just rabies carriers and don’t exhibit any symptoms of the disease?

A rabid bat might not be showing any symptoms, so you have to assume all bats might have rabies. That's why health authorities tend to say "just looking at a bat, you can't tell if it has rabies."

That said, daytime flying, obvious sickness, and aggression/biting are all symptoms of likely rabies in bats.

On average, yes. That particular person might be a terminal cancer patient, though.

Rabies has to be one of the absolute worst ways to die.

Nowadays, they will put you into artificial coma and then you die.

Not nice, but not really worse than many other modes of death - at least superficially. We do not know what happens in the sedated brains of the patients in their last days.