Is this fair?

[Darkness]

Alarm is an astonishingly useless defence. It is a 20ft radius emanation, so any attack that doesn't need people to get right up close and personal (e.g. sneak attack with ranged weapon from 30ft range) and it doesn't help.

Still, other than sneak attack, death attack is melee only - so if an assassin wants to use it, they'll have to come close.

 

[Plane Sailing]

Yes, a strange quirk of fate that alarm is slightly better defence against assassins than against other character classes.

I disagree with Merak's assertion though on the basis that if you want to get surprise attacks in on sleeping foes you are probably better at doing it from longer ranger - the closer you have to get in, the more likely they are to hear you and raise the alarm. A strike team of six rogues all using their sneak attack to shoot a guard could drop him from 30ft range with high effectiveness. Caster classes likewise are most likely to strike at the party from further away than the 20ft radius of alarm.

Alarm sees most effective use in dungeon settings IME.

Regards