Actually, YES!
Morellonomicon actually has a very unhealthy version of grievous wounds because it completely counteracts the things that many healing based champs rely on most: Being at low health for bonus healing.
BIG DISCLAIMER: The new EC and its upgrade are also bad iterations of Grievous wounds because they are too strong stat-wise.
That said, punishing a healing champion when they are supposed to be thriving is just counterintuitive game design. Of all the intrinsically healing based/drain tank champs (notably
), the majority rely on healing steroids that directly or indirectly increase when at a particularly low health level. This style of durability sets them apart as being specifically more difficult to DPS to death, while being more vulnerable to burst (If they're at 30% health and you can burst them to death in one go, they're dead. If you can only whittle away at their health, they'll sustain through it and kill you like they are supposed to do). Applying grievous wounds only to low health targets hard counters many of their core play patterns in an arbitrary and unfair way. Tell me, would you prefer to take 20% reduced healing at any health %, or take 40% but only below half HP? If you were a volibear, you'd know for sure that that 20% flat healing debuff is FAR healthier than 40% at below half, since the latter completely cripples his passive. That same train of thought goes for Aatrox's W heal, Mundo's ultimate, Zac's passive, or Olaf's whole dang kit.
That said, Grievous wounds across the board should be MUCH weaker, especially if they move to this healthier model of applying to damage at all health %s. Either some sort of stacking debuff (still capped low, say 25% healing reduction) or a flat debuff of at most 20% should be used. 40% is too extreme an amount and causes drain tanks to become excessively binary depending on whether they are grievous wounded or not during a fight.