Have fully completed this event now... was a bit disappointed that the copy from the exchange was not lvl 15 like the others but since she is only going to be a scouting tank for me that's not terrible. I bought 2 or 3 core packs during the event I honestly cannot remember now, but even if it was 3 that is the same as an 11 pull that only guarantees a 4* so I think it's worth it.