nittanytbone said:
Spot/Listen are pretty much worthless unless they're maxed out. A party facing a sneaky NPC or monster of an appropriate CR will only detect it with maxed out spot/listen.
This is true against the super-sneaky NPC, but most monsters (and especially monster groups) will lack in this area, so you gain a signficant advantage against them if you hear them a lot earlier than they hear you.
Still, I think one character with a good Spot and Listen check is sufficient, as is one with a good Search skill. Not everybody needs this skill, but someone should better have it.
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Climb, Jump and Swim (and to some extend Balance and Escape Artist) are a diffierent matter - you will need this skills to cover obstacles, and it usually doesn't help if only one can do it. But I don't think it is practical for everyone to have significant points in this skill.
Others must learn (and prepare) to help themselves with spells, magic items or by clever teamwork.
A Ring of Jump or Gloves of Swimming and Climbing might be useful in that regard - they can be shared by multiple characters (if at least one can clear the obstacle without it).
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In the end, I think no skill is neccessary for EVERY character (useful, yes, but not critical), but many skills are neccessary to EVERY group.