This seems a bit much. Not broken by any means, but given that there's a 1U 1/3 in M11 (the name escapes me) and it's playable in limited, this guy sounds like it clogs up the board way too well. Valiant Guard might be good in this slot, the whole +1/+1 counter theme might make him more useful as the game goes on.

the 1/3 for 1U is something that is only ever playable in weird formats (super fast ones, or core sets). Also, white is more of a creature color than blue, so it seems logical they're a little better at the 1/3.

This card, along with some of the other defensive vanillas, are here to encourage the "one big creature" style of play that Supply can create. I don't think it'd be a permanent mainstay vanilla guy, so we don't have to worry about power creep. In testing it's been a pretty average card.

This is better than Norwood Ranger and the white equivalent (and also Valiant Guard, not that anyone cares), but you're right, it's still only okay. It's a clever vanilla, in fact. Probably pushes the limited format towards longer games, which is an effect to be aware of, but it sounds like that's precisely what you're after.