Sorry it took me a bit to remember to check into this
The Infection thing is, as I suspected, a bit messy. The solution, oddly enough, may be to change Infection itself to just be "no healing" That will give the AI a pretty clear cut choice on how to handle it, no? Not sure I want to do that yet, but AI is always tricky for situations where it has to weigh "short term triage" (heal through Infection because OMG you're gonna die!) and "long term benefit" (healing it first, even if it means you have lower HP for a little longer because it didn't heal you instead)
As for the SP cost, I looked at the numbers and I admit I winced a little.
Here's how that apparently works.
1) If an ability and target combo's evaluation is less than 30000 (for reference, 30000 is a really, good evaluation, usually requiring multiple targets, healing a near-dead ally, or damaging a near-dead enemy to reach), and the ability user has at least half their health...
2) ..deduct 50% from the evaluation if the ability will drop you below maxAbilityCost * 2 Stamina...
3) ..deduct 75% (total, doesn't stack with #2) from the evaluation if the ability will drop you below maxAbilityCost Stamina.
I can easily see a 50% penalty being enough to override the difference in damage your Lilim would be getting with the situation you outlanded. These numbers are probably a bit too high, and I'm going to experiment with adjusting them. Thanks for the report.