In which case, and a genuine question here, why aren't you up in arms about the dragon just posted. If it was in 4e it would be the single most metagame-oriented monster in the entire edition. If it's a line in the sand, the dragon is way way over it. Legendary Points and the Ignore 4 spells/day are both raw metagame points.
If that's your line in the sand, Next has just not crossed it, but is busy playing volleyball over it.
I'm not up in the arms about Legendary Points and Ignore 4 spells per day because, as I mentioned before, it's a "work in progress" and it's important to me to give someone the benefit of the doubt when they ask for it.
The other reason I'm not up in arms is that Mearls already expressed concern about mechanical contrivances, etc. so at least I understand what the goal is, if not the final implementation. Conversely, if Mearls had opened the article with
a line about "process-sim nonsense" ala Obryn, I probably would've gotten up in arms.
Since it's a genuine question, I'll try my best to articulate why else. Not all these answers are created equally or full arguments in themselves for anyone else's playstyle.
- The DM doesn't have it to use it (I could trust a process-sim-oriented DM to use them judicially if it would otherwise be a problem for the gaming group's playstyle)
- It overlaps with other rules that I've already accepted, like saving throws and magic resistance and the fact that sometimes, magic just doesn't always work 100% against everyone
- How do I know if the dragon auto-succeeded on the saving throw or just rolled a successful saving throw
- It prevents a 'boss' monster from disappointingly dying in the 1st round and spoiling the climax
- It allows a DM to 'officially cheat' without having the DM feel angsty about fudging dice and feeling bad about it
- there was a whole preamble about legendary creatures bending reality so to speak. It's very Planescape-esque and also fits with the concept of hit points IF you accept that hit points is part luck and destiny. This pseudo-logic might be controversial (I haven't thought about it much further than that) but at least Mearls said something about a default story
- it only applies to the DM and the behind-the-scenes stuff that happens with a good magic show and it only applies to monsters, alien and legendary, and as is, doesn't seem like it would happen very often. It doesn't apply to the PCs themselves, who I try to relate to and understand. If it applied to a relatable PC that used a metagamey power every encounter power, it would feel more in my face
For me, the overall impression isn't that D&D Next is busy playing volleyball over that line in the sand. I hope that helps somehow?