Yeah... I realized that in S4 when we played one week of HC and got ranked on the 2p leaderboard. I mean not just in that one week, but we ended up being on the leaderboard at the end of the season. Not a lot of people playing at all (though those who are have created an amazing community, I loved the HC communities which were always helpful and seemingly free of trolls and... well... idiots ;-)).
I wish there was an incentive to HC; if there was, I'd probably play HC in S7. But with even the HC leveling removed from the season journey, there's just no point. Not sure what can be done about it, but it's rather sad.