I'd like you to familiarize yourself with Concentration and how important it is in 5e and then re-evaluate how sane Firebolt doing 2 to 4 ticks of damage is
Common, a flask of oil can cause 10 damage over 2 turns no concentration required. If you had a lit torch in your can argue that you can throw it as a free interaction, if not your friendly wizard can do that dealing a 1d10 damage plus the oil.
Is it shorter range, yes, does it cost resources - a paltry sum. Is it an example of persistent damage that does not require concentration.
