Item access can also be arranged at lower levels by virtue of having item crafters Roy. You can also break the game just by RPing, and asking for almost inconsequential favours. I edited that in later, I just take too long when posting/editing at times.
Orion, level 10 encounters are seriously 4 CR 10 stone golems. Your AC build dies like a chump under that.
Or, they grow a brain, and hide behind the Wizard, who is using Acid Cloud and Magic Mouth to kite the golems in a circle.
Level 10 encounters can seriously be a level 11 wizard who is waiting for the party in the last room of the dungeon; sort of how
every printed adventure is arranged. The last room always has not only a higher level creature, but usually one with a bunch of minions to delay the PCs while the BBEG spams SoDs on the PCs.
Either way, AC is useless at 'higher' levels.
Orion wrote: CR 11 Centipede: +18; CR 10 Scorpion: +21 CR 10 Giant +20/15/10. CR 9 Vrock +15/13, CR 10 Clay Golem +Motherfucking 14
Sure there's also Earth elementals (23 at 9, 27 at 11) and CR 11 Spiders +27.
+to hit does NOT scale smoothly by 3 per level. It DOES vary wildly within a CR, even among "brute" monsters. Your 27 AC WILL substantially reduce the incoming damage from most of these monsters. And if you fight lower CRs it gets even better. If your level 10 guy fights 2 CR 8 Stone giants, their +17 hits you only half the time, their second wswing only a quarter. At that point, since 32k into a +4 Amulet of Natural Armor does WAY more for you than buying moderate fortification.
The thing is, those numbers don't reflect everything. Those creatures will also have stuff like
reach on you, and more damage than is "assumed" that PCs can acheive with "melee" characters (not clerics/druids/wizards with buffs).
A Fire Giant, the +20/+15/+10 Greatsword deals 3d6+15 damage, and has reach on the PCs, usually meaning extra hits, plus the option to move back for more free hits.
That's about 27 damage per hit; meaning 4-5 hits and the average fighter goes down like a sack of bricks. This mythical "8-10" hits territory does not exist. The fighter that can survive that amount of abuse is
super optimized,
Super Resilience Territory:
-Having miss chance (maybe even stacking miss chance, by getting say, Cover, and stuff like
Displacement, and
Mirror Image, and say,
Blur just for kicks).
-Being something whose Con doesn't give a damn about enemy damage. Being 'changed somehow into a creature with really High con, or something, or just not giving a shit, and being a
Shambling Mound; and having someone in the party have a Shocker Lizard Familiar/Animal Companion/Pet/Pokemon. You've got a natty AC of +11, and you're only large and weird shaped, so you only pay x4 Cost of materials, and x2 Weight for armour (6,150 for mwk FP; 36k Mithral, 60k Adamantine). A Shambling mound seriously can get a Con of 77, minimum 300 HP at all levels; average Con is 2.5*60, putting HP anywhere from a min of 308, and average of 624, and a max of 984 hp.
-Stacking DR properly, then layering DR from different sources; Most 'core' way, is being a Were-Rat, and buying Improved Damage Reduction over and over again; and using a Bow; then being the party Tank, due to sheer DR, and lack of monsters with Silver weapons in most printed adventures.
Really, being able to soak 10 hits in a combat is "really hard" territory for melee characters, involving unusual characters, that most people wouldn't assume or consider. The best most PCs pull off if 3-4 normal hits before they die; even using Tome material. Using straight Core stuff; you're better off having a wizard cohort just to cast protective spells on you.
Well, more CR 10 'things'
Gargantuan Monsterous - It seriously doesn't care, it has a +21 to hit; Imrpoved Grab, and a Grapple check of +37. Unless you've got an Elf wizard with an Octopus pet who goes by the name "Der Crack Ein" (aka. the Grapple-Wizard), whoever gets grabbed is gonna get a lot of damage.
11-Headed Hydra - Yeah... not much per hit if you have stacked DR, but the sheer number can wear down PCs who have no or low DR.
9-Headed Cryo/Pyro Hydra - This flavour freezes/burns people with DR; and only slightly less dangerous in the raw damage dealt department. Only a PC with a lot of ER or DR (or both) can stand up to one of these.
Noble Salamander - It's got a Huge Fire Elemental 1/Day (ie. this encounter, first round action), and can cast 3 Walls of Fire (ie. it's next three rounds). Those spells are going to last the whole fight (15 rounds max); and PCs are going to take anywhere from 4-21 pts of damage every round from each Wall (On wall, 2d6+CL (15); within 10' (2d6); and 20' (2d4). Hopefully someone has a Resist Energy Prepared, or had a resist item. Most of this creature's danger doesn't rely in melee, but non-melee damage.
Juvenile Red Dragon - [sort of an outlier, Dragons are 'really' supposed to be 4 CR lower if used at 'random'] Still, it's a critter with +16 to hit; and 6 attacks (2d6 Bite, 1d8 2 Claw, 1d6 2 Wing, 1d8 Tail Slap; with +9 from Str), AC 26 is hittable; and only until you get to 31+ AC are you out of the creature's average to-hit range.
Also, it has an AC of 24 (aka, you're gonna hit this monster); it's seriously the size of a large Panther or Tiger; with wings; it's not Elephant Sized kitty tiem yet. Since nothing it seems, has an AC that's worth a damn anyway. So focusing on damage dealing is more win than focusing on To-Hit, or AC.
Anyway, Turtling does
not work as a viable D&D tactic, the mechanics and the rules and items simply don't support it.
Even most creatures don't do these things; instead they have defenses that are unusual, like Spell Resistance, or Spell Immunity.