That's an over-reaction, as not every party will actually have a character with chill touch, even if your group happens to decide to always include such a character because they specifically want to spend literally every round making sure no enemies get to regain any hit points.
No. It is not an over-reaction. I often wonder why I have to explain this. Here is the sequence:
1. Regenerating or healing creature.
2. Focus fire. Chill touch. Dead.
3. Next creature.
4. Focus fire, Chill Touch. Dead.
Doesn't matter if its a troll, Strahd, Juiblex, or the like. A cantrip makes regeneration, healing, and the like completely useless to parties that know what it does and ensure they have, basically nearly every party that understands the rules. It makes regeneration useless because as soon as they know a creature has some means of regaining hit points, chill touch will be used to shut it down.
The only resistance to this spell is immunity to spells of at least cantrip level. Otherwise anything that regains hit points in any way can be shut down long enough to kill it even to the point of waiting for it to be close to death.