House Rules
This discussion is becoming less and less about what you can achieve with Diplomacy in a hostile situation, and more and more about various house rules DMs use in their game to vary from the Diplomacy rules.
That's great that you guys have found house rules that satisfy you in your games. It's difficult to come up with good house rules sometimes, and I am genuinely happy you guys have found a way to do it with this skill.
This thread isn't about that. In fact, this forum isn't even about house rules. I'm asking for advice UNDER THE RULES AS WRITTEN for what you can do with a Diplomacy check in a hostile encounter (and perhaps that means this thread should be moved to the Rules thread).
The rules currently state that a DC 25 is sufficient to persuade the dragon that has captured you that it is a good idea to let you go.
PERIOD.
Now perhaps that is errata, and should now read DC 35 (since the DC to change something from Hostile to Friendly used to be DC 25, but was changed in the PHB to be DC 35). But regardless, the rule says a good roll on your Diplomacy check (25 or 35) is sufficient to persuade a hostile, superior target like a dragon to release you from captivity. Not save you for last. Not eat you quickly. But release you.
If you disagree with that rule, feel free to change it in your game. But I am really interested in how DMs who use that rule, as it is written, to handle Diplomacy checks in a hostile situation.
I'll admit that I wrote this chart under the AU rules, rather than the new 3.5 PHB rules. However, I think the new rules make Diplomacy MORE powerful, not less, given the new definition of Helpful (see end of this message).
If you hit a DC 60 with a single full round action (which includes the 3.5 -10 modifier to a rushed Diplomacy check), that changes your opponant from Hostile to Helpful, barring unusual circumstace modifiers.
What does it mean to have someone who was Hostile now Helpful? Granted, it doesn't mean they are charmed. But it should mean something. Heck, it should mean A LOT, since DC 60 is incredibly high.
I never said they will give you all their treasure, strip naked, and walk out of the dungeon singing your praises and doing good deeds for all their live long days. I never said they were a slave, or an automoton, or charmed.
All I said was they are now helpful towards you. In my opinion, that means they won't attack you or your friends, unless you attack them. It means they might help you with a task (depending on an opposed Diplomacy role for that negotiation). Is that unreasonable? Should you be able to do more, or less, with a Helpful target? How about for the other attitudes?
BTW, the new 3.5 PHB says "Helpful" means "Protect, Backup, Heal, Aid".