If they're going for the quad Last Ditch effort, they have all successfully wasted all their hat main ability slots. And not to mention, the perk only activates in the last 30 seconds, so they're really only banking on the comeback there. Which is a pretty bad strategy.
As if you can kill them in that last 30 seconds (it shouldn't be that hard because the buffs are minor), you take about 7 ish seconds away from their 30 seconds of going ham. But honestly, they're setting themselves back if they do that.
But if you really want to hard counter the strategy, take a risk and wear respawn punisher to reduce their effective last ditch effort time. But other than that, just make sure you don't die in the last 30 seconds, or just pick off their members if they overextend. The boosts only apply to ink recovery, ink saver main, quick respawn and ink saver sub. So, they're not going to have much mobility or damage over you.
Hope this helps