I think they could make Shen better at being the counter to auto-attackers or maybe just generally anti-physical, as opposed to Galio being anti-magic, because I find his dodge zone to be far more interesting than his Q and yet more power is put into the latter
but that wouldn't really fit Shen's theme of duality, would it?
also ult doesn't provide a shield, it gives the ally he jumps to his W's damage resistance
as a quick edit, I still think Shen should be a fighter and not a full tank; it'd be a lot more interesting to see some fighters with supportive/defensive-minded qualities, and it'd probably be easier to balance his damage output vs his durability that way.