By that same logic, we should have more champions with Yasuo's Wind Wall mechanic in case we want to counter skillshots, or team untargetability to counter point-and-click skills, or a mass cleanse to counter crowd control, and so on. There is a vast amount of mechanics in this game that can be pinpointed and isolated, that does not mean other champions need to be built specifically to counter those mechanics. Moreover, there are preexisting mechanics that already are well-equipped to act as counters: burst applied in quick succession tends to work well against persistent sustain, for example, because it can kill a target before their healing really kicks in. Targeted disables can do a great job of preventing supports from laying down clutch heals, and displacement can help isolate that support, or a target in need of healing. Just because a mechanic isn't assigned a label saying it counters X mechanic doesn't mean that such a counter does not exist, and generally I think League would do well do rely more on these subtler and more general counters, rather than hard counters like Grievous Wounds.
One of the reasons I also personally advise against increasing the presence of targeted counter-mechanics like Grievous Wounds is that they tend to make balancing harder in the long run, and often make champions countered by those mechanics even less healthy. The increasing prevalence of GW is largely responsible for increasing the amount of healing across the board, for example, which peaked during the enchanter meta of last season, where their healing and shielding were inflated to such high amounts that marksmen became practically impossible to kill. This problem still persists to a lesser extent to this day. The harder you push against a specific feature, the harder that feature has to push back to remain balanced, and that typically leads to a situation where, in absence of that counter, the feature in question easily becomes overbearing. This can also be seen on champions like Zed or Malzahar, who suffer in metas where their counters are common (e.g. Stopwatch/Zhonya's and Cleanse QSS, respectively), but who are otherwise tremendously oppressive against targets who don't buy those counters. In a game environment where QSS didn't exist, Malzahar would never be allowed to have his current play pattern around his ult, for example, and that would likely be better for everyone.
is the single best AP item in the game.
is an 800 gold counter to any heal reliant champion, and it builds into 
for late.
is a counter to every heal reliant champion except 
and it builds into 
.
and have it up every fight if they don't want any of these.
is sometimes more than necessary.
apply Grievous Wounds or something?
