All values placed here come from https://playtera.co.kr/news/no…from=1&sub_type_cd_from=3 and the Information ingame available:
So the new card event only grants normal cards via Event Tokens. We will need at least 80 normal cards per rare partner card, since 2x20 normal= 2x10uncommon=1x10 rare (not to mention that chances for critting this style of card fusion is rather rare).
This implies that we need to farm at least:
-80x5=400 normal cards for all rare cards.
-40x5=200 normal cards for all uncommon cards.
-20x5=100 normal cards for all normal cards.
This gives a total of 700 normal cards to farm throughout the event period of 28 days. Since we only get a quantity of 1 card per login chest (compared to KR 5 per login chest?), the login will give us 28 normal and 28 uncommon cards (if the quantity does not change over the time period). Assuming you do not get a higher quantity then 20 cards of any kind from login event this will leave us to farm 700-28-28*2=616 normal cards. Since this is not a multiple of 20, we assume that we will have to farm at least 620 cards through Dungeons/Vanguards.
-Dungeon<501 will drop 1 token and give 1 token via Vanguard so 2 token/(<501 Dungeon)
-Dungeon>=501 will drop 2 tokens and give 1 token via Vanguard so 3token/(>=501 Dungeon)
This leaves us to farm at LEAST 207 Dungeons of type >=501 in 28 days or 8 Dungeons/Day and knowing that chances for getting a higher grade of cards using fusion is not very good (seems to be less then 50% winning channces) this number is definetly only a lower bound. I assume that one has to farm at least 12 dungeons of type >=501 per Day with avg fusion luck to get all fragments from the Event.
This is not reasonable and GF should increase the number of fragments from Login or they should increase droprate. Also for future events: Give us a direct possibility to exchangne normal for uncommon or rare cards without RNG. Tera has more then enough RNG and we do not need RNG in grinding Events, too...