You are right, there is actually a big difference between using a martingale in a pvp game and using it in a dice game, first of all, the notable difference is that pvp games like the one duelbit just launched is a game that comes with a zero house edge, and also, In some pvp games, your skill is what determines your wins and loses, though there are still some pvp games that are purely luck based.

But for the dice game, it's completely a luck based game, using martingale on such games is something I personally would recommend, it's one of the fastest ways to lose money, regardless that one could win big money if he or she is lucky while using this strategy, but in essence, I have not come across any gamblers who has a good testimony about martingale.