I stopped here, because I want to break something down for you. At least from how I see things.
"Punished" boils down to having to use GCDs on non-offensive skills. SCH being the primary barrier healer of the group suffers the most from this as both Galvanize and Catalyze status effects are tied to GCDs. By having the 'penalty' of using GCDs for support instead of damage taken away (very similar to WHM lily mechanic), you are basically asking for even more DPS uptime on SCH. This basically tacks on 300pot damage to the enemy each time the SCH uses a barrier. You need to understand that this makes SCH ridiculously OP, or they would have to make pot adjustments on their other skills to compensate; OR they disseminate those high potency increases for SCH among all the other jobs making them wonder why some of their skills had a bit of potency shaved off of them.
Ideally, the green-DPS SCH would love to spend all their aetherflow skills on Energy Drain, and when you cross this line you're basically making them a watered down SMN with the ability to ST/AoE Earthern Ward on demand. You probably can see where I am going to go with this.
Proceeding onward, Savage/Ultimate peeps would have to crunch hard numbers for you comparing SS to CO. For me, the fact that I can place SS wherever I want while on the move completely trumps any potency advantages CO has over SS. There are also intangible factors at play. As an example, most players see a beneficial bubble and think, "standing in this = good"; in contrast, not all players are aware of the residual effects of CO, and if you truly want to optimize CO, all players have to be in its radius when you fire it off.
Not everything is as it appears on paper. If you spend a good portion of time playing both AST and SCH, these things will make themselves known to you, and you can truly decide which one your playstyle favors. And that is really what it comes down to. Things like SS vs CO isn't going to make or break or party comp, and are supposed to compliment each other during an encounter. SCH shields are THE PERFECT example of how healer GCDs should be used. They feel really powerful and beneficial, so you don't really give a thought about the loss to DPS.
Free healing is actually a problem, and a big one at that. It, along with the lack of DPS skills are the two biggest contributors to healer boredom. SCH isn't getting Ruin IV; see above comment about the watered down SMN.