Potential good options (while preserving Witch Bolt's theoretical infinite duration)
- If it remains an Action, then upcasted damage should probably apply to subsequent turns, not just the initial damage. At 3rd level, you'd deal a guaranteed 3d12 damage against a single enemy, which is comparable to Call Lightning's 3d10 damage to enemies in a 5-foot radius, Dex ST for half.
- You should be allowed to jump the Witch Bolt to a new enemy once the first one dies.
- It could be moved to a Bonus Action damage on subsequent turns, but the enemy gets a Dex ST to halve the damage to balance that out.
I think I’d be happy with either option 1 or 3, but suspect 2 might make it overpowered. I’m okay with some spells really only coming into their own in specific circumstances, such as single, high HP enemies, as long as they’re not a downright terrible option to have at hand more generally.
