Hey, so I adore the Staff of Explosion, not only for the reference, but its design, and the idea behind it. That said, however, I think it's actually kind of underpowered currently. As it stands, with a full mage set, FAR more Mana than the base game allows, all the magic buffs I can think of, etc., a full-charged hit (about 12 seconds of standing perfectly still) will deal 55000ish damage single-target. Now, yes, that's a lot, but it can't really 1shot any bosses in mid-late game, which you'd think it would be able to given how hard it is to use. If you're moving at all, or grappled, etc. that charge time, as far as I can tell, increases at least fivefold. Additionally, at half-charge or so, it only deals around 10k damage. That's about 6 seconds of standing in place. Add on that it's literally impossible to fully charge it without using a full bar of mana (I have again, far more % reduced mana use, and over double vanilla's mana cap, and it still takes nearly 3 bars of mana completely to full-charge a single shot) so you waste multiple potions AND fire it off with Mana Sickness since even holding the full-charge takes massive amounts of mana... It's just not a good weapon for when it's obtainable (Post-Plantera Dungeon earliest).
Some possible ways it could be improved:
1. Make charging it a bit faster, perhaps. Say 10 seconds for max charge?
2. Stop the "primary" target circle from moving upward for around half the charge time for some reason. (I assume this is a bug)
3. Make charge time while moving/grappled/etc. less horribly slow. Maybe 1/2 the rate instead of... Whatever nonsense it is now.
Yeah, not all that accurate to the source material, but this is a fast-paced game.
4. Make holding full charge not consume additional mana. You already put the energy in, why is just keeping it there taking even more?
5. Perhaps change it to always use 99% of your mana bar at full charge (to not activate Mana Sickness), and scale its damage off of how much mana was used.
Then maybe give like, a minute debuff of -50% mana regen rate and -50% max mana as compensation, to truly get that "wow that was too much energy to put in one attack" feeling.
Say you have 200 mana (basegame max with no mage gear or buffs) it does 50k~ish. 300? 100k~ish. 400? 200k! 500? 400k!! If you have mods that allow you to get such insanely high amounts of mana, you're probably needing higher damage outputs anyway by the time you have it. The whole idea of the staff is for it to be a pain to charge but be a 1shot-kill to basically anything, anyway.