Is our group using the Sleep spell wrong?

Question

I am playing a 3rd-level wizard, and I have to say sleep seems really overpowered as a spell. On numerous occasions now, a combination of sleep followed by the rest of the party slitting throats has seen us clear enemies really quickly.

I even used it on a charging bugbear getting him to pass out just before he reached me, we then managed to take him down to just 4 health in the next round of combat before he woke up. And a wolf who was clamped onto the leg of a PC.

Our GM does have creatures wake up as they take the wounds, but 9 times out of 10 they are already dead, given that they can’t defend themselves from the stabbing. Are we doing something wrong here with this spell? Having spoken to other wizard players, they have told me they find it a pretty useless spell.

Answer 1

Maybe, possibly, most likely not.

It is widely agreed by most people that Sleep is a very strong early game spell, the fall off due to the fact you roll for HP, but there are a few things to keep in mind.

1. You can target allies on accident depending on how you arrange AoE's; the spell is not friendly to allies.
2. You have to roll 5d8 and go from lowest-HP monster to highest, meaning you could roll and get an 8, and that group of six goblins... is now just five goblins... and one of them will use their action to shake their friend awake.
3. Those who are affected by the spell instantly wake up to damage or, as previously mentioned, their allies shaking them awake.
4. Stronger monsters (with higher HP than you have rolled) could just flat out resist it, in the case of fighting a lone owlbear or other high-HP monster, meaning you have completely wasted your spell.

With those restrictions in mind and the fact a Wizard only gets 4 level 1 spell slots a day, 2 level 2, with the average adventuring day being 6-8 encounters... it can fall off fast.

However most people do not actually do 6-8 encounter adventuring days, so it could just be a case of you feeling it is a lot stronger than it actually is because you always have spell slots up.

As a side note on your mention of other wizard players saying the spell is useless, I imagine they only play mid-tier/after level 6 or so as Sleep is fantastic early game. The average HP amount is close to 20 and with careful placement you just took out 3 goblins with a single spell.

In conclusion: Enjoy the spell while you can; it only gets worse.

Answer 2

Possibly

Based on this part of your question

we then managed to take him down to just 4 health in the next round of combat before he woke up

Per Sleep's description, the unconscious condition lasts until the affected creature takes damage. Then they would be conscious but prone. Unconscious creatures are attacked with advantage and any attack that hits is critical. After the first attack, attackers within 5 ft are still at advantage but they don't automatically crit.

And a wolf who was clamped onto the leg of a PC

It would be impossible to not target your friend in this case since the PC and wolf are grappled and sharing a space. If the PC has fewer current HP than the wolf (quite possible if they've taken damage), they would absorb the spell's HP first. Then there may not be enough HP left to put the wolf to sleep too. You would also need to account for anyone else in the AoE. During combat, it can be difficult to not target friends if they are in melee range.

As far as the overall effectiveness of sleep, I concur that this spell loses it's first strike effectiveness as you go up in level and begin to face higher level enemies. That doesn't mean it doesn't have it's uses. But the more and higher level the foes, the less likely you are to clear the field with sleep.