If there really were a lot of bots in that giveaway, I think that the Duelbits team will analyze this and make appropriate changes in the upcoming events. As an option, I guess Duelbits could add a captcha for participants to confirm their participation in each giveaway. Of course, any kind of captcha is unlikely to stop abusers, but at least it can reduce their number.
They will have to manually check the suspicious account and bot activity so they don't give much attention but yes sometimes there are certain restrictions like submitting your ID as well and some other cases which can reduce the spam bot participation in these kind of giveaways but still we see lot of them trying to rush whenever such codes drop on Twitter.
That is a long process as well, it is not like they can do it in a single second via some software, they will have to do it for a long time and it takes time to do it right as well. I personally believe that the best thing to do would be making sure that you are doing the right thing and in order to do that you need to take time because the right way to do it takes time.
I haven't had it happen to me here, but it did happen to me in another place where I had to wait 48+ hours for my withdrawal, and I was fine with it because I knew that I did nothing wrong, and the rules were on my side, so I just waited and I got it eventually, so it worked out well and if you did nothing wrong it will work out for anyone.
actually I didn't really hope but if given why not use it no one will refuse 
