Grievous Wounds items don't feel fair to play against.
TL;DR: Doesn't feel interactive due to duration. Reduce the duration, add maybe another item/reduce other items healing effects.
Not because of what they do, though. It's because of how grievous wounds is applied and the duration. Now, I don't really play champions that make use of healing abilities, but when I do, seeing any of the three grievous wounds items built against me feels like a big ol' kick in the nads.
There aren't many options here really to stop healing effects, so to compensate they're given huge durations. But these durations can just stop certain champions from functioning without the need to even focus on them.
Morello's being the biggest offender - Deal any amount of magic damage just once when they're under 35% health and their healing is gutted for a whole 8 seconds. 8 SECONDS. That's such a ridiculous amount of time, whilst requiring only one source of magic damage to hit. It'd be fairer if it even started at 50% at 3 seconds. Atleast then, you have to actively reapply it as opposed to hitting them once.
I believe there was a discussion on increasing the price of executioners a while back because it was too effective at gutting certain champions, for such a cheap price. I think it's fine to have a cheap grievous wounds effect, but it shouldn't last 3 seconds from one application. 1.5 seconds would feel much fairer to play against, and is fairly easy to keep applied with just auto attacks.
Maybe if the durations were lowered, you could have another grievous wounds item, hell, maybe healing effects on other items wouldn't need to be so high either.
I don't know though, hardly a balance expert, but does anyone else feel like grievous wounds lasts far too long for very little interaction?

thought items or kit, can a real bummer to fight if played well and regen/ls back to full health in mere moments. there's others as well, like a fed adc with lifesteal but you get the idea.