We're changing rapiers, thanks for the catch.
Sleep is, well, sleep. The target instantly falls asleep. It's a fictional condition, like much of Dungeon World. It's up the GM, who is (per their agenda) portraying the fantastic world, to portray. The amount of time depends on the circumstances. In combat, it might only last a few moments, until the sleeper is stumbled over or stabbed. If given to a nightwatchmen doing a boring duty watching the walls, though, it might last minutes or more, if no one disturbs him.
Daze always takes effect, at least for a moment, but casting it on someone the fighter's about to stab is pretty pointless. They'll stand and drool, get stabbed, and then pop out of it. It does let the fighter just deal their damage, or let the thief backstab them, though, since the target won't be fighting back. It's mostly for taking someone out of the fight so you can focus on others. (I also just modified it a bit, so it only effects lower level creatures.)
As for how both of these work on groups, that needs to be clarified, but I think they don't, really. To daze a gang of goblins, you'd need a roughly equal number of casters. To poison a warband of orcs, you'd need a dose for each. I'll make that clear in the rules.