When it comes to deckbuilding, this event card is almost nothing like Loyalty. The difference between complete mono and just the mark is enormous.
However, thanks to vaults being relatively small this late into the War, it's hard to field anything but a mono if you want your own mark. Why? Not enough off-element pends or alternative means to gain quanta. To add to that, taking off-element pends isn't very practical in the long run. Luckily, being able to convert more cards per round makes them much less limiting.
Either way, if we limit almost every event card to specific rounds, there won't be much randomness left. Yes, some event cards are almost useless in certain rounds for several teams, but not every event card has to be that specifically balanced either. This one, for instance, probably won't make any difference whatsoever.