That's the reason of the 1 specific - 2 random. Making it 1-1, no one would use it. It's too weak and with 10 quantum pends you would maybe never ever het 4 or 5 quantum of an element untill the oponent kills you. It's matter of power balancing and comparison with the existing cards.
2 element pendulums = 1 of each pilar, counting every 2 turns.Pros: get both elements you want at the same speed. Cons: 2 and only 2 elements per pendulum.
2 3-1 quantum pendulums = 1 element pilar and 1 quantum pilar, counting every 2 turns. Pros: No element restrictions and guarantee getting the mark quanta you want. Very very likely to get.
6 2-1 quantum pendulums = 3 element pilars and 2 quantum pilar. Pros: Has no element restrictions and still gets random quanta. It must have cons. The cons are that 6 of them produce an amount of quanta equal to 5 cards, as the normal pends produce quanta equal to the same amount of pilars.