If you give dicebitcoin the ultimate benefit of the doubt and assume that there was a "rogue employee" you still have to take into account that they let a random untrustworthy person access their code and thus jeopardize all users on the website. This is the best case scenario, when users trusted you on Just-Dice, they did so assuming you wouldn't do something like that. In my opinion this seems pretty damning. I don't see why a rogue employee would choose to steal in this manner either.
Also, why would someone in that position want to sabotage that website when their potential gain from having that sort of access is so great. He could literally just view the serverseeds and win millions while remaining undetected. The only reason for something like this to occur is to boost the profit of the website.
Yes, trusting random new people to change the site's code is crazy.
And I really don't see why anyone would chose to rob a few users in a very obvious way when they have the option of stealing using the seeds in an invisible way, forever. People don't seem to care if the site's profit is at 0.3% instead of 1% - it's easily explained by variance.