When is metagaming too much as a DM?

[Zanticor]

Taking the risk of being scolded I would suggest that you are all looking at it from a weird perspective. D&D is not about fair challenges. Facing a Balor is about an iconic end fight. So lets make it cinametic. If you are looking for how far you can go without being an unfair dm you seem to think you are bound by the same rules as your players. Which is kind of strange because a dm operates in a different league. You are above the gods in our world so you can decide what happens. There is never a fair fight only bad luck or bad judgement from your or their sides. This means you should look at those hitpoints and decide if:
1. your guys need an extra round or they are done for: Target the barbarian with no effect.
2. You know the spell caster will one shot your balor and cut your end game short: Shoot the guy.
3. The fight is almost lost but the mage still has a chance to save the day: Blast the good for nothing cleric and gloat about how his god isn't there to save him (hope he's not to close because the balor is about to blow!)

See metagaming is your duty as a DM you just have to make sure your not to blunt about it. You know you will always win in a fair fight (lightning strikes you down from the heavens and you all die). The hard thing is faking being beaten fair and square all the time while taking them to the brink.

Zanticor

 

[Runestar]

Thanks all for your invaluable feedback and replies.

Anyways, I had a casual chat with my gaming friends, and they said that they didn't really mind or care. If anything, their tactics are based on the assumption that the DM knows their characters inside out and will metagame along that line (ie: the wizard guesses he is the most likely target of any fort-based or power word spells and will prepare the appropriate countermeasures, like starting the day with moment of prescience, or using heroics to get that maneuver which lets you sub a fort save for concentration check).

So that apparently gives me a lot of wriggle room with regards to how much I can afford to go all out vs the party. Well, that sure was a relief to know. I wasted a good worry.