One chain demon would wipe a 1st level party out. Several would be a nightmare.

Anyway, as far as rogues vs. clerics. If the rogue got the jump on the cleric, then maybe, just MAYBE it could take the cleric down. Except probably not.

Clerics generally gain about 1 point of AC from dexterity. That's plenty for their eventual adamantine fullplate. So they don't lose much flat-footed, and a sneak attack is just slightly more likely to hit than a normal attack.

If the rogue gets the jump on the cleric and remains hidden enough to take the cleric down over several rounds, then the rogue wins. Unless the rogue is a UMD whore (high points in Use Magic Device and loaded down with scrolls and wands). That's the best situation for the rogue, but the cleric might still win.

A high level cleric spends one round buffing themselves, and the next round leveling Tokyo (putting the "C" in the term CoDzilla). In a straight fight, they will dominate a rogue. And a straight fight is what you're going to get after the rogue makes his first sneak attack.