ClaytonCross
Kinder reader Inflection wanted
ClaytonCross Fiendish Resilience is PHB standard 10th level patron fiend warlock feature.
I looked up after you last post. That is a specific type of Warlock though and while I grant you its an ability that makes them good against dragons its a strength of that specific player character not a weakness to dragons.
You can certainly presume dragon surprise as standard, but i myself have seen more stories of dragons and such in both fiction and games tent to treat adult dragons and lairs as not anything subtle, more like environmentsl hazards affecting the locale. That combines with terrain preferences seems to me to make "i choose fire" a reasonable daily chouce.
If you have for shadowing of the dragon and time to rest this very specific anti-element ability does make the fiend warlock good against dragons AND all other known elemental enemies. I play a warlock of the old one it is not helping him at all. So basically you found a build gear to be a dragon slayer and your saying that since the character is good at killing dragons that dragons are week. That is a false argument. The Dragon is not week the PC your describing is strong against them. The exact same build of warlock with a different patron and a non-fire resistant race would be destroyed. If I were building a character to be a Dragon hunter this would be a good build...That is really what you a have proven. Not that Dragons are underrated.
Also, of course a GM can add anti magic, spells, armies, waves of beholders as they see fit to a dragon's package as he sees fit. That just does not do much to say the baseline MM creature is this or that or the other... Except maybe to support the idea it needs beefing up by GM.
I would submit that its not unusual for dragons to have mentions or at all against a dragons intellect for it to have used a mage to setup trap in exchange for letting the mage live. This debate point is about preparations. If players are being balanced against a dragon counting their preparations then the Dragon doing the same particularly in its layer... is common since. Your not balancing players or dragons at this point but just preparations that the GM allows. That is my point. Their is no need to add to a Dragon but if your not letting the Dragon prepare defenses in its home, then your basically saying the fight is a surprise and the players don't get on ether. --- I will grant you that your Tie-fling Fiend Warlock choice for Dragon slayer would me smart to have Resilience set to cold combine with Fire from TieFling so even a surprise attack in a part of 4 that build is likely to do well. Not that it will do any good once the rest of his party is dead but that's to my point that this is an uncommon build that is strong against these creatures.
I can prove it... Give me the design of the rest of your party... I bet not one of them does so well.... You picked your strongest option because that's what people do to prove a point but also because it is uniquely skilled for this kind of fight it also shows that the Adult Dragon needs a special type of PC to be truly threatened. A Barbarian totem worrier of the bear has resistance to all damage but is not likely to have ranged attacks of 100ft which is the required attack range to engage a dragon using the tactic I described of Dropping 40ft from 100ft "strafe" its 60ft fire breath then fly back up 40ft out of range of many ranged attacks.
The same warlock has to take eldritch spear or the spell sniper feat to be able to engage an Ancient dragon using the same tactic from 130ft with its 90ft breath attack and would be an appropriate solo challenge for a party of 4 level 17 characters. Again you could build for this but ...if you did not build to fight at extreme range vs elemental damage your in trouble.