Seriously, 2 health every 5 seconds doesn't seem like it's worth anything at all, accounting minion aggro would already outweigh this mastery so much. In about 5 minutes of play time you would regenerate about 120 extra health. This seems pointless when a skill can knock out that damage in .5 seconds
Tier one masteries aren't made to make big impacts on the game but rather make small adjustments. People building defenses might get a few extra MR or armor out of the Unyielding mastery but other champions would obviously benefit from having that small amount of extra sustain. It doesn't seem like much but it still adds up in the long run. Also things like this help to negate DoT damage especially DFT so it's not completely useless.
Most all the masteries are only small statistical improvements.
Recovery only gives 2 health every 5 seconds but the enemy's Sorcery only removes an extra 2 health every 100 ability damage. Vampirism is only 2% as well. Butcher is 5 flat damage to creeps only and the benefit of that mastery can fall off pretty hard.
Alternatively, over 5 minutes you would regenerate about 120 extra health. 
is 150 extra health. So for mitigating harass, you are effectively getting 320 gold of extra health for those 5 minutes of laning by taking this mastery.
It obviously won't help in hyper aggressive lanes where you're constantly taking damage but if you're in a passive lane or atleast a safe lane it's good for sustaining through laning phase over time
A minor buff to 3 hp per 5 seconds would be fine of a buff without making it too op with competitive with other T1 masteries too weak.
