Should I have bought Oblivion Orb on Singed?

I just got flamed in a game for building oblivion orb on singed. I was the only heal cut on the team.

https://preview.redd.it/4735vkwemofe1.png?width=993&format=png&auto=webp&s=4be6a129b6a7191379ba89bbb234765f61fbd2b7

If avoidable, I wouldn't have bought it. I thought their team had too much healing from Hec and Yuumi and my team was unwilling to buy one saying "singed you have ult". For clarification, singed ult is up every 100 seconds (every 3 fights early, and every other fight later). In hindsight, I probably would've skipped the heartsteel, but I stand by my oblivion orb buy. But since 2+ people on my team flamed it, I'm wondering if it was the wrong choice.

The item says it reduced 8k healing at the end of the game but I'm not sure if it includes healing that would've been reduced by ult.