About the Hextech items.

I like ... but alot of the times I can't understand it's purpose when exists

One can argue that makes it worth it but i dont see it. I don't understand why the active's Slow decays in .5 seconds but the passive one doesn't. Sure the health u get back from casting can offset the 100 health u gain from Rylais but still.

For 200 less gold you get an insanely similar item to with less AP, Less Slow, a Makeshift active. I just dont understand what does help me accomplish? I can build , Hit Multiple projectiles and have an extremely useful (engage,disengage) passive, cdr, same health. I can build a For even better healing self healing that's not mana dependent, better active damage, better slow, a little bit of AD for those few Casters who have AD scaling/relies on auto attacking. You could argue that does a better job at helping a mage kite (multiple targets)... than all the other hextech.. but its a single decaying extremely short duration slow on a 40second cd? I mean yeah it does do damage... but aren't even allow to hit multiple people? So the active is just a Mage version of without the sheen? I'm just really trying to understand the purpose of this item's active effect.

What would be cooler to me is if the item actually 'freezed'... or Bound/Root an enemy into place for .5-1 seconds (Not stun and based on distance) . It'd not only make this item unique in a sense, but make it worth buying it for some champs over Because then it's actually giving them a tool to survive/attack while sacrificing hp and ap, and doing something the does; which is Adding something actually unique and innovative in the item pools for mages.