chriton227
Explorer
You wasted a 3rd level slot that can be used for something else on 15 points of damage. That's why not. You don't do it unless you have no choice. You think it's smart when a dragon breathes on you for 59, 29 on a save, you launch a 3rd level spell for 15 points in return? You don't do that. Not smart at all.
Okay, looking at the numbers, Fireball will average 28 damage, but with the automatic save will be knocked down to 14. Fire Bolt, giving you the benefit of the doubt that you are a L11 caster, will average 16.5 damage on a hit and 33 damage on a crit. Against something legendary, a 50% hit chance wouldn't be unreasonable, netting an average of 9 damage. So Fireball will do on average 55% more damage. If you are only a 10th level caster, the average for Fire Bolt drops to 6, with Fireball doing 133% more damage on average. You didn't ask if Fireball was smart, you asked why someone would use it. If someone's primary concern was doing damage as fast as possible without regards to burning through their resources, Fireball is better than a cantrip. After all, what good is having a level 3 spell slot left if you get killed by a dragon that has 5 hit points left?
Fireball isn't a smart overall choice in this situation though; it is a spell optimized for use against groups, not single hardened targets. Then again, any wizard that thinks going toe-to-toe with a dragon by trading poorly chosen spells against the dragon's most fearsome attack is a good idea isn't very smart either. And this isn't a wizard problem, I can't think of any class that would fare well in that situation.
No. You don't make a choice. You cast fly to get the martials into battle. Period. Concentration getting broken? Tell me how you make a concentration check when you just took 60 points of damage and the DC is 30 and you get a +3 to +5 on the roll (if you took Resilient? Tell me again about worrying? No, it's going to get broken. Improving your defenses? How? I have a staff of power, bracers of defense, and Mage Armor. That is a wizard's defenses. My AC is 19. Tell me how I can improve them? I cast shield when I need to. AC 19 is nothing to high level creatures. Easy to hit.
You're completely missing the point. It's about choosing between my having fun or the martial having fun. Our strategies are effective. That's why we're still alive. Sorry, it's not fun as a player to cast fly and then launch a cantrip a bunch of times. It's not fun at all as a wizard. Those are my options otherwise the martials sit on the ground throwing javelins with disadvantage.
Defenses are more than just AC. You shouldn't be standing in the middle of an open field engaging a dragon, that is a battlefield so heavily slanted in favor of the dragon's capabilities that it should eat you for lunch. Cover is your friend. Partial cover will get you +2 or +5 on your AC and reflex saves, and stacks with your shield if you cast it. Full cover is even better. With the change in movement rules in 5e, you can come out of full cover, cast a spell at the dragon, and then go back into cover before it can act. If it is something like a cave opening or doorway, it may even have to come down to the ground to be able to attack you at all. If it can't attack you, there is no need to make a concentration check. If you can find some narrow areas (clumps of trees, narrow alleys, tight crevices), you might be able to force it to land to engage you with attacks other than the breath weapon (it can't fly if it can't spread its wings), in which case the situation will be better for the martials to engage to draw attention away from you. Spread the party out so that it can't get the majority in a single breath. If you cast fly on a martial to let them get into melee with the dragon, why and how is the dragon breathing on you instead of dealing with the martial that is in their face (the breath weapons are usually much shorter range than your spells)? Or it may be the time to retreat and reengage at a later time in a location that is better or when you are better prepared.
The martial's player is using you as a crutch to cover their PC's shortcoming at the expense of your fun instead of finding a way to deal with it themselves. This is a problem with the player of the martial character, not a problem with the system or the spell. No rule in the system says you have to put the fun of the martial's player ahead of your own fun, and in my view the martial's player is being pretty selfish with that expectation. There is no excuse for a L10 martial to not have a better ranged weapon than a javelin. Even if they used Dex as a dump stat, they have a decent proficiency bonus and a bow or crossbow will have a long enough range to avoid disadvantage. Maybe the martial should look into acquiring a potions of flying or winged boots (either through purchase or through questing), a trained griffon as a mount (expensive, but what else are they spending gold on), or picking up an ability score increase or feat that could improve their ranged capabilities. Character design involves tradeoffs, but in this case it sounds like the martial sacrificed ranged ability in favor of melee ability, but then expect you to suffer the negative consequences of the tradeoff instead of dealing with it themselves.
You're level 3. Get back to me at level 10. I was having fun at level 3 when sleep was effective, saves were low, and the yard trash wasn't hitting you for 25 points an attack, while having 50 to 70 hit points each while you're still launching 8d6 fireballs. Legendary Creatures are an entirely other matter. It's not real fun when the dragon breathes on the party for 60 points and a Con save, follows it up with a legendary action tail slap for another 10 to 15, then drops a lair action on your for another 10 damage doing anywhere 55 to 85 points of damage in a single round. Then he gets to start hammering you with physical attacks.
The gods help you if he gets lucky on a breath weapon recharge and gets to breathe twice on the party in two rounds. You might as well prepare to make a new character.
I'd like to get some context for your experiences here. What legendary creatures have you been encountering? I've gone through the MM and I didn't see a single creature with Legendary Resistance below CR13. Only about half of the creatures that are CR13+ have legendary resistance. I assume that this is so casters won't be having to deal with Legendary Resistance until they have a reasonable number of spell slots available. If your party is fighting legendaries that are 3+ CR above the average party level, and fighting them on their home turf (where they get lair actions), it should be brutally difficult. Assuming 5 PCs and a CR13 legendary this is between a hard and deadly encounter to start, and beyond deadly once you take into account the situational advantage of the lair. This is the sort of fight that if all possible you only want to go into if you are well prepared and have a good plan of action, and if you aren't there is no shame in making a tactical withdraw. If your DM is adding Legendary Resistance to creatures that don't normally have it, or creating lower CR legendary creatures and giving them Legendary Resistance, this is an issue with the DM, not with the game. Why is it that the dragon is focusing so much attention on your wizard? And have you talked to your DM about how you don't find getting steamrolled by a higher level legendary to be much fun?