Actually, this example is why the CR system sucks. And perhaps even an argument against D&D's historically steep number scaling.
Nope, that's not the issue! A Salamander Noble is perfectly appropriate as part of a threat for a level 10 party. It's simply the nature of the design. Salamander nobles don't have the action economy to really be a threat to the party on their own.
One attack per round against one target will never threaten a party unless the attack has a high likelihood of inflicting instant death. Period. There are just too many ways to cycle players out, get out of combat, deny actions, and recover from even VERY hard hits on a single target that only happen once per round.
The only way to challenge an entire party is multi-attacks, multiple actions within the round structure, AOEs and zones, and other effects meant to acknowledge the multi-target nature of the encounter are necessary.
When you have five or six monsters doing that, well... heh. Good luck resolving combat in under 4 hours. "Each monster acts twice per round, and... hmmm... there's a trigger when they're bloodied, and they lay down a zone around them... the zones stack, so if you move there you will take 5+5+5+5 fire damage... unless you take a different path, then you move through that zone... and that zone... and... oh, you only take damage once per round per zone, so you don't take double damage there, but that is a different zone..."
The design is completely, totally different between 1 monster encounters and multiple. Even 3E knew that - every monster designed to be encountered on its own had breath weapons, iterative attacks, magic, and other multi-target features.