Zz'rot's portal needs... more.
- The voidlings are extremely squishy.
- The voidlings do little to no damage to minions.
- The damage increase every 4 voidlings is too long inbetween.
- No combat stats, which is fine.. if the item was gold efficient/actually excelled at its job.
- In most "safe" locations, due to their uptime, the voidlings can only siege one tower.
- Voidlings sometime ignore inhibitors.
- Portal itself, while being immune to skillshots, die extremely fast to any AD champion.
As an item that's supposed to help tanks with little to no waveclear splitpush, it doesn't really excel at it. Most tanks in the game don't have reliable waveclear, so the first few rounds of voidlings die trying to battle minions. This makes the initial voidling and probably even the 4th voidling never reach the tower you're trying to siege. So then you have to wait another cycle to even get the returns from your tanky items.