Unless you have some kind of huge rube goldberg combo costing a million XP, this thing is a giant trap.
On one hand, a 3 cost weapon that can get you +4 to hit is great. Where the problem starts is that it only deals 2 damage and exhausts itself. 2 damage is not enough. There are somewhere around 100 enemies in the game with 2 or fewer health, and that number includes swarms and bosses that get +X per investigator health that I can't be bothered to count, because there are around 250 enemies in the game with 3 or more health.
An investigator dedicated to fighting needs to be able to deal at least 3 damage per round, full stop.
The best case scenario for the sickle is to deal 2 damage, evade the enemy, then finish it off next round with the secondary ability to clear the doom. For four xp you're doing in three actions, with three tests, across two rounds, what any other weapon/spell could do in 2 or less. All that 4xp gets you is an unnecessarily huge bonus on the first of your three tests, and it still requires outside boosts to seal the deal.
There are two cards that make the sickle work, and they're both expensive. The first is Elle Rubash, who makes sitting on the doom while you wait for the second attack less dangerous, and gives a small but appreciated bonus to make the secondary attack actually connect. If you dual-wield them you even have a relatively stable combo... for a bank-breaking 10xp minimum. The elephant in the room is that, if you're running Elle, Abyssal Tome does what the sickle does at half the cost. It lacks the extra boost for the first attack, but makes up for it with the ability to boost the damage output when you really need to. Unlike the sickle, it is appropriately costed for the limitations involved.
The second option is to spend a whopping six more xp on Sin-Eater. Sin Eater lets you double tap the sickle in a given turn, and gives an option to clear doom that doesn't involve using the terrible secondary ability. It's pretty good, as should be expected for a 10xp combo... ignoring the caveat that you can't use it at all in the last three rounds of any agenda. I wouldn't spend 10xp on a combo that still regularly requires a Moonlight Ritual, but you do you I guess.
The sickle is just worse in every way that matters compared to the Enchanted Blade, a card which already doesn't get much play because it's not a spell. It is laughably worse than every other 4xp weapon or spell. The only investigator in the game that would want to take the sickle over something else can't, because it's 4xp. You could argue it's less useful than a Kukri, a level 0 weapon which is cheaper, more flexible, and doesn't add doom to the field, and kukri is the worst card in the game.