I think marks count a little more than a pillar for the reason they are already in play.
When Quanta Index calculations were made, the pillar was counted for 5 (quanta) because that was the average number of uses a pillar get (counting turn of draw, turns of permanence on the field, length of game, etc...).
A mark is worth the same number of turns the game is expected to last.
So if you expect to finish the game in 5 turn, you would use the mark 5 times so in this case it would be equal to a pillar.
An average game is 10 turns, when using a stall deck it can be 20+ turns.
So i think the QI should be calculated accordingly.