I shouldn't have been so worried about the Rammstein tickets. Sure enough they sold out in minutes once again, but in the end we got the tickets. In the end I actually got tickets for the both days as my youngest one afterwards told me they had also acquired tickets for me and them. Luckily for a different day.
Sure there is an active aftermarket for the tickets and they would no doubt sell fast if needed. But I don't mind going twice.
I have to admit I was impressed with the ticket sales system. The site didn't go down despite huge traffic spike. There hardly even was any slowdowns. The only issue with the system in my opinion was when there were only some odd tickets left, freed from the carts of people who cancelled, the system showed occasionally somw tickets available, but no matter how fast you tried to add them to your own cart they were already gone once you submitted the order. It would have been nice to have some sort of queue system for those as well.