A simple change to ZZ'rot's Portal to make it a better tank item

Currently, it's got:

50 armor 50 MR +100% base health regen

Passive:Point Runner Active: Spawning voidspawn

Health: 40 Armor: 115 MR:20 Health/Level: 15 Base damage to minions: 30 First and every 4th voidspawn gain bonus of 100% of armor/mr as damage.

The key issue here is that that 4th voidspawn can be easily targeted and removed as the first priority. Not only that, but a tank that stacks health to combat true damage (against, say, a Darius), gets a reduced benefit to the minion's power. To make it a more useful item for every tank, I'd add an additional buff to it.

First and every 4th voidspawn gain bonus of 100% of armor/mr as damage and 20% of bonus health as health. This way a tank who builds bonus health actually gets a benefit from building health that ends up penalizing him against anyone with % of max health damage. A tank with 1000 bonus health would get a voidspawn that's not only has some damage to it, but is durable and not one hit-able at range by any carry build worth a damn. A 1000 bonus health tank at level 18 would get a voidspawn with 500 health (still less than that of a siege minion at level 18), instead of the paltry 310 (less than that of a melee minion), which at level 18, are virtually 1-hitable.

Thoughts?