100% dodge chance not working

Recently played a game, in which I built 100% dodge chance veigar (yordle 6 bonus + Trap Claw, Quicksilver, Dragon's claw). In the fights it still got hit and killed by autoattacks (no wild bonus, nor any true dmg item on the enemy team). Since there is no visible dodge chance stat available, I assumed dodge chance is additive, as it makes the most sense to me. In practice thought it doesnt work like that, and I dont know if it is a bug, there is max dodge chance cap, or it is not additive.