Why Zzrot portal isn't pick often, semi long read inside.
Now Zzrot portal isn't built on champions very often because it is not appealing. Sure it gives a whole bunch of armor and magic resist along with bonus health regen, but that isn't enough tied in with its passive and active.
Problems with Zzrot: The stats it gives are not that appealing outside a select few champions.
Yes it gives a whole bunch of Armor, Magic resist, and health regen, but the passive and active tied into it aren't worth it. The bonus move speed around turrets and portals is ok I guess and the portal to split push is alright but those aren't appealing enough to pick it up.
Why?
The portal minions die too quickly and don't really get the job done unless you are right at their turret having the minions suicide onto the tower, or you have a portal in your base to hold off the supers, or maybe you try to put the portal in the middle of the lane(or inside a bush by a lane) in which any player with half a mind or a team that isn't behind will go and take out the portal.
Want to know why some other tank items like Zzrot who give no health but a lot of armor/mr have that Zzrot doesn't have? A fairly decent passive that make them worth picking up.
Sure the move speed by turrets and portals is nice but that isn't really good in combat unless you are select champions who are monsters with move speed in either kiting them away(Zzrot Garen) or impossible to catch(Zzrot proxy Singed).
Examples of other items similar to Zzrot but with more appealing passives.
Has a fairly nice amount of armor, gives very nice cooldown reduction, great bonus mana, and a great attack speed slow aura which makes it optimal for champions who are either mana hungry, scale really nicely with CDR, or both.
I don't want to talk about this anymore, I wouldn't pick this over Zzrot anymore unless you are a 500 armor Rammus or Malphite or the enemy has no magic damage in which this is cheaper. Passive was good before it got nerfed which was why it was a good pick because you were able to fight ADC's and damage them for critting you for over 800 damage.
This has similar Armor and Magic Resist as Zzrot but the passive(active?) is so good that Zzrot doesn't stand a chance. Who needs to split push when you can have a second chance at the game?
This item is similar to Frozen mallet in mana, cdr, and armor except this passive is constantly and visibly making an impact in the game. An aoe slow being spammed every 2 seconds is amazing, people would rather build this item than Zzrot not only for the better stats, but for the great passive.
The pattern with these items is that they all have a reason to be picked for their amazing passive/active that is far better than Zzrot because they actually have impacts in fights.
How could you change Zzrot?
This might sound crazy, but you could nerf the armor and MR for health. Tank items are useful if they give health in addition to resistance stats unless they have great actives/passives(see above).
You could make the minions last longer, spawn faster, or refund 50% of current cooldown on zzrot if it gets destroyed by an enemy champion so we aren't standing there twiddling our thumbs for 2 and a half minutes until we can use it again.
Or the craziest idea is that you could allow the player to destroy their own Zzrot portal in 3 auto attacks to gain 20% of their max health back(different life bar from what the enemies get to destroy it).