It's an odd spell to commit to using every turn, even at low levels.
Who are you going to use it against? If you're fighting against something dangerous, you're better off casting Magic Missile or Chromatic Orb every turn for a significant increase in damage. On the other hand, weak enemies die before this spell can get enough hits in for the 10 turn auto-hit to pay off. I think the auto-hit is what makes it suck, because there is no point in committing your action to weak guaranteed damage for 10 turns against a single target.
Basically. The additional consideration is that level 2-4 wizards are spell-slot limited. Witch Bolt's strength is
supposed to be that it can deal auto damage each turn without costing additional spell slots, which will help wizards last through the Adventuring Day. Of course, this doesn't really matter in BG3, which makes the spell practically useless.
Especially given that spell-slot preserving is less relevant in BG3, I'd be in favor of buffs to WB.
Restrictions for Witch Bolt- Witch Bolt deals damage over multiple turns, so it should do less damage in a single turn than any other 1st level spell.
- As an Action, Witch Bolt needs to be preferable over Cantrips. It achieves this mainly by dealing auto damage (if you succeed on the initial cast).
- It requires concentration, which means it needs to have sufficient power to be a viable option over other concentration spells.
- It needs to be worth the opportunity cost: i.e., if an enemy dies in 2 turns then you'd be much better off slot-wise by just casting cantrips, or casting any other 1st level spell + a cantrip.
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.
