Mixing services are based on trust. If you do not trust them, do not use their services. There are many services that provide a lot of reliability.
If you use them to hide your id (privacy,) they use Cloudflare, so it is best to think carefully.
With regard to whether they are scammers, until now nothing has been proven, but they have locked their topic and they may turn to scam^[1]. If you do not want to gamble, do not try them.

[1] https://bitcointalk.org/index.php?topic=5168505.0

I have no idea where you got this information from, because when you try to access the site everything works fine. It looks more like you are distributing FUD.
If you really saw the website database for sale on the darknet, please provide evidence in the form of screenshots or links to the sale.

It is probably best to not use a mixer in the middle of a DDOS or when you are receiving error message when trying to access their site. Once the error messages stop and when the DDOS is over, all else being equal, there isn’t any reason to not use a service you otherwise would be willing to use.

Unless the person on the DN site is offering proof that you can independently verify, I would assume it is unsubstantiated as long as it is a single person on a single site.

But currently the page is available!?

And the problem with the too small wallets has already been solved in another thread. Maybe it's all just coincidence. But if you are unsure, you should use an alternative mixer

So, what would that Db consist of? Are we sure it's not a scam darknet listing?
A good mixer wouldn't keep any logs that could identify users or transactions. Even if they did, what else would be in that Db that could be of value? Any specific vulnerabilities of this specific mixer that would contain information of any value?

OP is a little conflicting as the title talks about a Db and the content of the website source. Even if true, maybe the darknet market listing could be a troll.

If it's true {which seems not to be} then a Data Base of a mixer would contain random information of logs, letters of guarantee, sessions IDs, and even IPs. But any mixer is  supposed not to save those data or even run servers.
Only governments and institutions fighting money laundering would be interested in that Data Base as they can trace logs and addresses but this is far to purchase it from dark web marketplace.
I doubt if it's true to find such a strange offer as vendor should be conscious about potential customers for his product. Why would anybody purchase a hacked data base of any mixer?
I agree that op is either trolling or spreading faud .

I am also able to access the site but I would not use it for mixing in the period where there is a fud of hack. I do not want my funds to be handed over the hackers and why would we use this site when there are other trusted mixers sites available. Let the situation settle down and then I will decide if I should try smartmixer or not.

Their last message is about them having to fight off a DDOS attack so this would explain why they're down. If the attack appeared before the weekend it's even more likely they won't be able to get it fixed before Monday.

There's no proof that their database was leaked. Many times people were trying to scam buyers who wanted to obtain leaked data. Trading with thieves is always a bad idea.