Is Ohmwrecker a useful item?

No. Only time I've used it is playing AP Udyr and soloing towers with it but other then that it's pretty much useless. If a nautilus can tank 32 tower shots without dying (as seen in pro play) then who the hell cares about disabling a tower for 2-3 seconds.

it's situational for splitting or succeeding at sieges/dives. i think it's a midgame item.

I know it and see it alot but i cant ever justify picking it because even though it has an okay active its stats are worse than zhonyas compared to its active and its active isnt even half as good.

active is weak, not even good as a first item buy to early game towerdive.

however in terms of gold/itemization its well above average. (iirc it comes out to being something like 114% gold efficient) but because its a cheap item its just weak all around and sold later for literally any other item.

basically the active doesn't justify you buying this item over any other combat oriented item like sunfirecape or deadmans plate. (even randuins is better). so do you really need a 4th hp/armor item? (sure CDR is great but its easily accessible these days via cleaver, frozen heart or spirit visage,

I honestly don't even know why this item still exists.