being able to summon 6 useful skeletons a second would be pretty hard to balance
Immersion, fun and consequences >>> balance.
Seriously. Just look to VtMB. Nosferatu is far harder than any other clan and if the devs had made the deformity just a -1 seduction instead of a crippling curse, or removed it would be far more balanced but would made the game far harder. Firearms in other hands, on the beginning, you have just a awful .38 special revover which is ok vs unarmored humans(vampire hunters generally use armor) but awful against even the lowest of supernaturals. On late game, you have a .338 LM scoped rifle, flamethrower and firearms become a easy mode(BTW, vampires are weak against fire)
Talking about firearms, fallout new vegas limited the usage of grenades(25mm and 40mm) by making then hard to find, available in few supply on vendors and costing a lot. Anthem limited by cooldowns... That said, cooldowns are a thing normalized on rpgs that rarely exists on other games and on the new contra for eg, everyone is criticizing they putting cooldowns on weapons.
powerful spells you can only use once every 5 minutes that need to be used strategically, summons you actually need to keep alive instead of throwing away like garbage, emergency defenses
Games with cooldowns become a every-time same rotation spam, not a "strategic game". And you are assuming that the unique way to have strategic use of spells and other things is via cooldowns. And are not. Pick D2 iron golem for eg, to craft a iron golem, you need to sacrifice an item. The golem absorbs the item property.
Other example is Dragon's Dogma MAker's Finger, a arrow which can OHK anything but the toughest bosses and costs 300k gold and exists in a ultra limited quantity. Or Sacrificial Bolt for MAgick Archer, is a insane deadly blast of darkness but you need to sacrifice a companion to use the spell.
Divine Intervention on M&M VI~VIII was clearly the strongest healing magic ever but aging the caster was a huge toll to be payed. Moon ray could only be used in outdoors at night. Sharpmetal is only deadly at CQB.