Did anyone see the dead men plate and boots of swiftness on leona?

She comes at you like a truck and it is freaken fast truck that is to damn tanky with strong cc its ridiculous. I use my q to slow her down (lulu support) to get rid of the momentum but it stacks up so fast that she is gaining the movement speed back and on top of that she has boots of swiftness which reduces slowing effect. What is the point of boots of mobilty when this item is now in the game? Boots of mobility gives a total of 125 move speed while swiftness and deadmen plate give 120. While mobility takes 5 seconds of no combat(attack or even you attacking) to get the instant movespeed. While deadmen plate needs cc to get rid of it (attack doesnt work) and the movespeed builds up while stacking. The two items litterally outshines boots of mobility on top of that its super helpful to tanky champion.