>>280769733 (OP)
It depends on existing party composition/how much control I have over setting the rest of the party.
Fern will slot decently well into any party setup. She has good attack, good defense, a little bit of utility. Solid, reliable mage... but thats it. You could replace Fern with any other "pretty good" mage and get largely the same result. A hundred other wizards can do what Fern does. A thousand.
Megumin's explosion magic offers something unique. No one else is going to do what Megumin does, which means that with Megumin we can solve problems that no one else can solve. Like any gimmick build, you have to make sure that the rest of your party is built with it in mind: we need a big focus on defense and crowd control of small targets, because big targets eat the Explosion. Dungeon-centric abilities are worthless, because we want to be engaging our enemies out in the open, etc.
A properly designed party built around Megumin as the cornerstone is a terrifying thing. Or a party that is already functional enough that they can take on Megumin as a party member, knowing that most adventures she might not be able to do anything but saving her for the few times they absolutely need her. But in a small party as the only offensive caster, she's a liability.
