AaronOfBarbaria
Adventurer
I think there is something fundamentally different in the way that you and I think about NPCs, because I basically treat them as a one-time use challenge morsel that is built to fail, so them not being tuned so that their concentration spells are reliable doesn't register as a problem - just like their chances of surviving the party being low doesn't register as a problem, because they are there to be defeated.Remember....I'm looking at this as a DM in the context of NPCs.
And I think it is entirely shortsighted to try to consider only this one context of a spell when deciding if it is good enough as written, especially since most NPC options don't even involve spells, and the NPCs can just as easily use stoneskin like a PC party should (put it on the beat-stick while the caster aims at avoiding damage to maximize its effect while minimizing concentration loss chance).
The only "hoop" being jumped through is asking yourself "when is this spell useful?" and not trying to force the answer to be "always, no matter what." since that isn't how any spell in 5th edition actually works - they all have situations they are excellent in, and other situations where they don't even remotely matter.Again...seems like having to jump through hoops to make this spell useful.
This is likely just difference in our personal experiences, but you have labelled the most common types of damage (nonmagical bludgeoning, slashing, and piercing) as being a "very narrow range."So...we have a spell that is a 4th level slot, takes up your one concentration slot, costs 100gp a pop and only effects a very narrow range of damage (non magical bludgeoning, slashing and piercing). Compare it to other spells of the same nature and power level and it seems to me it doesn't come close. Protection from Energy is pretty much an identical spell, is only 3rd level and doesn't cost any wealth.
Yet you bring up a "pretty much identical spell" that is lower level and doesn't have a costly component as though the two are equal. They aren't. Protection from energy applies against far less common damage, and since you have to select the type of damage from a short list you might not pick the most useful type or might not even have many monsters you face while it lasts actually use that damage type - but bludgeoning, piercing, and slashing? Really good chance you run into monsters that use those, and that it is nonmagical too, unless your DM is specifically selecting from only a narrow band of monster intentionally to limit the damage types being dealt.
Immunity is a bad idea because it makes certain character types unable to contribute and misses the entire point of why concentration can be broken through damage in the first place.Again...I think my preference would be to make it give invulnerability or perhaps resistance to all damage until 10hp/slot level has been absorbed then the spell ends. That way it's more of a sure thing, it is more unique and worth that 100gp cost. It can still be concentration.
Resistance to all damage? Well, sure... if you want stoneskin to be hands-down the best buff spell on the books, that's the way to do it.