I got to ask Sirhcez what he thought of Zz' Rot portal on stream today
His response was "I dunno man this s--- is pretty useless"
He was playing Nasus and they ended up winning either way. .
So it looks like there isn't much point to building it on those who want farm or do not need more "tower-killing" power, but it is an extremely strong tool if many players purchase it on the same team or if a heavy waveclear or siege champion like 
or 
purchases it.
If you purchase it on a fighter who can already push/melt towers quickly enough you are probably better purchasing a combat-based item since the main advantage ZZ'P provides isn't utilized that well. .
There have been a lot of threads complaining about the item being Over-powered, which may just be because players have not discovered effective counterplay to the item yet, as it goes with many new champions or items.
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As a tank main I am very very happy Riot is wanting to give more love to non-bruiser tanks (as tanks have pretty much been the laughing stock of ADCs and 
recently) and give them more split pushing capabilities but I haven't decided if this was the optimal route to do so or not.
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Anyone care to discuss?
and 
. Their AR/MR boosts can make the banelings that come out of the portals hurt like crazy.
), which is a neat aspect of it.
and 
would only buy it as a final item
and his bonus health passive.
Sion could build: 
Get free health from lanes he isn't even in ... and jungle for more health.
because he is a strong split pusher already. Adding 
I personally would buy