spellcraft/detect magic vs illusions

[Sir Draconion]

whats the point in casting illusions at high level if the other guy knows what you are casting because of high spellcraft or setting a illusion trap and being discoverd with a detect magic

shouldn't there be a will save to detect the illusions' magic before the chance to scan or spellcraft it
or are the spells just useless a high levels

 

[shilsen]

Spellcraft would only apply if the caster is in plain view, and the PC has to choose to use it at a given point. If someone wishes to use Spellcraft against an existing effect, it takes a standard action, and there is not always time for that. If the spellcraft check succeeded, I'd give the PC a +4 bonus on his Will save, but that would not automatically dismiss the illusion.

Detect Magic takes concentration and time before it provides useful information about a spell or spell effect's school, so it's hardly useful in all situations. Also, just because you know the ogre charging you has an illusion aura on it doesn't mean you know whether it's a complete illusion, a human under a change self spell, or is carying an invisible kobold sorceror on its back. If it's a trap, I'd give the same +4 bonus to the save.