I entirely misremembered their press release about them migrating away from unity for an upcoming game.
This, of course, needs to be checked by community feedback on changes to the game because perfect balance doesn’t always equal fun!
The Fireball spell in D&D is a third-level spell, which means a spellcaster can get access to it at level 5. Compared to other third-level spells, and the power curve as a whole, fireball is overpowered since it does a large amount of damage over a large area, but it exists in the space it does because it's such an iconic and evocative spell/ability that feels so fun to use when it really hits that the designers want people to take it and use it.
That is to say, the spell is so fun to use (which I can confirm) that it's worth being unbalanced if it means more players get to experience it.
If one specific weapon or weapon combo became too popular with a too high win-rate, it usually got nerfed or the others were buffed.
You can see all the changelogs in the game.
Sometimes the changes were very simple and minor % buffs/debuffs: https://s3.amazonaws.com/i.snag.gy/etLjaJ.jpg
Sometimes the ability was changed to make it harder or easier to use, or to remove some OP side-effects (e.g. shooting laser would slow you down too much, which in this game it's also an advantage, as you can brake and avoid collision using the laser).
Achievements were just the earliest iteration in games.
There is a ton of better balanced deck builders out there. Personal opinion but monster train is much better balanced.
