RAW is one factoid for success, and one more for every 5 you succeed by. About the only wiggle room is which one to reveal first.
I'm not sure about that. Here's the RAW:
SRD said:
In many cases, you can use this skill to identify monsters and their special powers or vulnerabilities. In general, the DC of such a check equals 10 + the monster’s HD. A successful check allows you to remember a bit of useful information about that monster.
The way I read this, a successful check identifies the monster
and tells you a bit of useful information. For example, if a character made a successful knowledge check against the base DC for a Medusa, I would tell them that "this is a medusa, a foul and malicious creature with snakes for hair that hates other living things and surrounds herself with a menagerie of petrified creatures of all sorts
and the snakes are poisonous and the poison drains the life out of you". i.e. you would get the basics about the monster, plus something (per the RAW) "special", meaning not obvious and not revealed as part of identifying the monster. Frankly, any other approach seems extremely harsh, given the basic DCs for other uses of the Knowledge skill:
SRD said:
Answering a question within your field of study has a DC of 10 (for really easy questions), 15 (for basic questions), or 20 to 30 (for really tough questions).
The scale only goes as high as 30. Knowing that a bodak has a death gaze is not a really tough question.
That being said, I base the Knowledge DC and results on context and don't use those rules, because they make no sense (how easy it is to know something about a creature has nothing to do with how tough it is, IMO, only how commonly known it is).
In any case, I think most parties should be able to tell that a Medusa can turn them to stone by the time they face one.
It seems like your "common sense" is more "all players and PC's have read the Monster Manual" than anything else.
No, it means that not all knowledge is covered by Knowledge skills. I think most anyone living in a D&D world knows that red dragons are evil and breathe fire, regardless of their Knowledge ranks. I also think that most anyone knows that you shouldn't touch a cockatrice, or that you need silver to kill a werewolf. It's on the same level as knowing that snakes are sometimes poisonous or that cats hunt mice and purr. Those creatures exist in this world. These sorts of things are either DC 10 Knowledge checks or simply assumed. The monster identification rules are a supplement, to tell you things that are not common knowledge like which monsters have SR or which elements a bodak is resistant to.
By your logic above, though, whenever our brave, bold L17 team sees a monster, we should all join hands and Teleport away (or we should all be fast enough to flee at better than 60', and should clearly do so). Then we should upate our entire repertoire of spells so we are specifically defended against this one entity, at which time we return. It, of course, will have done nothing in the interim. And we always have a full day to retreat, review and revise our repertoire - never any time pressure, of course.
Well, that's what they should do if they aren't already ready to kill the monster. More than likely they should have death ward on hand. Or maybe they can just sneak a cleric in and have him turn it. Or they could just leave and let it go, depending on the scenario. But yes, that's pretty much how high level D&D works: face things on your terms if at all. If the banshee is smart, it will have moved on.
I find it interesting that, in all the Great Snake Debate, no one has mentioned the change from 2e to 3e where poison stopped being SoD and went to the new Ability Damage mechanic. Clearly, someone decided that the SoD was excessive, whether for comparison to real world poisons or for game design reasons.
I think it was more a question of filling new design space. I would guess that they came up with the concept of ability damage first, and then asked "hey what are some things that should cause ability damage?" and then saw that poison was a candidate. In any case, it's not an SoD per se, but it can in some cases disable or kill the character independent of hp.