How do you play around a Hecarim with Predator?

I'm a support main. And I'm not sure how to deal with a Predator Hecarim who dives the ADC.

I put wards in a bunch of places and get advanced warning that he's coming so we position a few people between the ADC and Hecarim.

I get a Knight's Vow and a Mikaels Crucible (for that fear).

I shoot CC at him when he gets in my range. I also dump my kit on the ADC if it isn't CCing the Hecarim. Also, I've tried saving my CC until after his ult is down.

I make sure our team is in a wide open area and not the tight jungle spaces when we start fights with Hecarim nearby.

He just ults in and becomes CC immune (his ult can't be stopped by CC and they often buy Mercurial Scimitar) and kills the ADC anyway. There's nothing we can do. CC doesn't work. Damage reduction and CC removal don't work. Wards don't work. Intelligent positioning doesn't work. And this is with the uber protection supports like Lulu and Janna. It's much much worse when I play a sustain support like Sona or a pick support to pick their squishes like Leona or Blitzcrank.

The only thing left I can think of is telling the ADC to buy and sell stopwatches or buy a Zhonyas Hourglass. But there have to be real ways.