It is the go to spell at 3rd level. It’s a gigantic leap in power and my first choice unless the campaign specifically restricts it. Since I play sorcerers and evoke wizards it’s not suboptimal unless I am encountering fire immunity monsters or environments that specifically negate it. It is S tier.
Slow, Hypnotic Pattern, fear etc?
Read the new DMG more. They're saying be very careful with encounters where PC are out numbered 2-1.
Xp budgets you can't really get up to large numbers anyway without using fodder. And vs fodder you don't need fireball anyway. Convenient I suppose but you've basically won already just by turning up.
Alot of hit point inflation in 5.5. You get fireball at 5, by 8 encounter xp budgets are 5-10k. If you use a few enemies hp totals are 80-120ish CR 3-5 depending on the monster.
CR2 is 450xp. Hit points are 50-60's it seems.
At level 5 xp budgets are about half of 8.
Fireballs not really worth upcasting but Raw by the time you get it the HP totals are high. Sure you're not really expected to kill them but depleting a monster of half its hp or a 1/4 still leaves them alive. 5E monsters hit hard. That's still a lot of incoming damage.
DM pretty much has to use CR 1 to hit large swarms by xp budgets. CR1 and lower has terrible saves. Leaves the very open to getting wrecked by whatever.
Most encountersvin WotC adventures top out at 1-2 npcs per player. Often less 1-4 critters.
10 ogres pr any other CR2s (allosauris, bandit captain etc) is a low fight at level 8 high at 5.
A low or medium encounter (cake walk in 5.5 tbh) has to use fodder RAW.
Very narrow window level 5 and 6 really. Assuming DMs using encounters remotely close to RAW. Ideally they're clumped up, not fire resistant etc. And even if all those boxes are ticked you don't really need the soell vs other options.
Yay.
And the spells not really worth upcasting.
Getting hot with fireball still sucks. Player HP totals are 3.0 levels still. Lots of healing though I've had level 7 pcs tank the equivalent of 4-5 fireballs (glyphs, exploding barrels and zombies). It's just damage. Hold spells, fear, slow etc will usually attract a counterspell. Fireballs a maybe.