I remember that time I turned on dedup on our 45drive box with 32GB of ram and 140TB~ of data..
Over time it would become horrendously slow, I agree, since you have too little RAM by a factor of at least 8.
I've got 30TB of small files stored on our TrueNAS system at work, there's no benefit to enabling it but if someone decided to toggle it we'd quickly learn there isn't enough RAM in the world to handle billions of 1-16KB files....