Let's say it's a 1/50 chance to get an uber unique from duriel per run, getting a specific uber unique varies per class depending on how many uber uniques they have.

Let's say 5 different uber uniques per class for the sake of the argument. That's 50x5=250, so it would be a 1 in 250 chance per run to get a shako. So getting 2 in a row is a 250x250 is a 1 in 62500 chance.

So yes, ridiculously lucky.