User blog comment:YourPrivateNightmare/Discussing the new defensive mastery tree/@comment-3148314-20150626104712

My opinion is actually contrary to yours: I find Legendary Guardian too situational and Adaptive Armor really strong.

LG only really helps in a teamfight. I'd only go that far down the def tree with champs on which I stack resistances anyway. Imo, when you fight less than 3-5 enemies. It's not always worth going all the way down in the mastery tree to get it.

While Adaptive Armor might not be that great on general bruisers that will build allround-resistances, it is pretty useful on champs that strongly focus on one type of resistance (e.g. Malphite, Taric, Rammus, Galio), because their skillset provides corresponding benefits.