I'm new to D&D and was confused by this: "It also costs a bonus action, and the caster cannot cast a spell with their main action on the same turn except for cantrips."
Are you saying you can't do a spell as your main action if you use a spell as a bonus action? Or just healing word? I don't find where either is stated in the rules, though I could easily be overlooking it. Or maybe I'm misunderstanding you entirely.
It's in the rules for spellcasting. If you cast any spell with a casting time of one bonus action then you cannot use your action to cast another spell that turn except for a cantrip with a casting time of one action.
I think a possible exception to this rule is a spell with a reaction casting time. Maybe my understanding of reactions is wrong, but it seems to me that they exist outside of any conception of turns. Also it's hard to know exactly what is more specific here for purposes of specific trumps general. I think the reaction trigger is more specific than the restriction on casting spells. So it might be possible to cast three spells on your turn, but I digress.
You are correct ReAction is different. There is a Sage advice on it that states.
If a Wizard casts a Fireball, then a Sorcerer uses thier Reaction to Counterspell, the Wizard can then use her Reaction to Counterspell the Counterspell.
I think a possible exception to this rule is a spell with a reaction casting time. Maybe my understanding of reactions is wrong, but it seems to me that they exist outside of any conception of turns.
If you cast a spell as a bonus action, the only spells you can cast that turn are cantrips with a casting time of 1 action. A spell with a casting time of 1 reaction isn't a spell with a casting time of 1 action. You can't cast reaction spells on the same turn that you cast a bonus action spell. After your turn ends, you're able to cast reaction spells again.
In practice, the trigger for reaction spells almost always happens on someone else's turn unless you're deliberately throwing yourself off cliffs with Feather Fall or provoking an opportunity attack and relying on Shield.
Also it's hard to know exactly what is more specific here for purposes of specific trumps general. I think the reaction trigger is more specific than the restriction on casting spells. So it might be possible to cast three spells on your turn, but I digress.
The general rule is that you can cast a spell with a casting time of 1 reaction when the trigger occurs. The bonus action casting time rule creates an exception to that rule.
Regarding the original post, no house rules in AL and Healing Word doesn't need to be heard.
I don't have a problem with Healing Word and it can't always be relied upon. A monk character died in my current Tomb of Annihilation game. The player chose to go with meat grinder rules and got surrounded/left behind to tank a gaggle of ghouls. That was with three other players able to cast Healing Word (and they cast it a lot in that battle). Also the actual tank was also getting wrecked so the Healing Words were spread around.
Sorry. If it wasn't obvious, I was referring to a post by Technoskald above.
You are correct ReAction is different. There is a Sage advice on it that states.
If a Wizard casts a Fireball, then a Sorcerer uses thier Reaction to Counterspell, the Wizard can then use her Reaction to Counterspell the Counterspell.
And so the Fireball goes off like normal.
Page 12 of this SA-Compendium: http://media.wizards.com/2016/downloads/DND/SA-Compendium.pdf
Thank you both! I had missed that. I don't think we've actually handled it wrong, though, since cantrips are allowed in those cases. So much to learn!
If you cast a spell as a bonus action, the only spells you can cast that turn are cantrips with a casting time of 1 action. A spell with a casting time of 1 reaction isn't a spell with a casting time of 1 action. You can't cast reaction spells on the same turn that you cast a bonus action spell. After your turn ends, you're able to cast reaction spells again.
In practice, the trigger for reaction spells almost always happens on someone else's turn unless you're deliberately throwing yourself off cliffs with Feather Fall or provoking an opportunity attack and relying on Shield.
Regarding the original post, no house rules in AL and Healing Word doesn't need to be heard.
I don't have a problem with Healing Word and it can't always be relied upon. A monk character died in my current Tomb of Annihilation game. The player chose to go with meat grinder rules and got surrounded/left behind to tank a gaggle of ghouls. That was with three other players able to cast Healing Word (and they cast it a lot in that battle). Also the actual tank was also getting wrecked so the Healing Words were spread around.