While not typically good compared to the other masteries, it's still potentially powerful.
When most champions start the game with 500-600 HP level 1, and you can only get 23 HP from scaling seals level 1, 64 from flat seals, and only about 40~ HP from the defense tree level 1 - getting an additional 50 effective health level 1 can actually be extremely strong.
For similar reasons red pot was good, it lets you gain a health advantage in a level 1 or 2 all in that can decide a lane.
The problem is that it's so deep in the defense tree. It would be nice if it was a 1 point wonder somewhere in the 9 point tree so you could take it over, say, 1 hp5 or something insignificant (it would take 4 minutes 9 seconds for the 1 hp5 to heal 50 HP, vs. getting a 50 HP shield level 1).
It should either be 1. removed, 2. moved to the 9 point tree, or 3. buffed to the level of the deeper trees to warrant picking over swiftness/legendary guardian/etc.