Honestly I would not go to change the GCDs but I would go to add OGCDs. The smn currently does not have many. I would thematically change Fester to something more coherent. I would free the carbuncle from the transformations and I would add some OGCDs in addition to the shield, perhaps even offensive. I would free up the phoenix OGCD heal which currently works only because the level designers are doing a big job to make the heals more or less always match a boss aoe. In reality I would also free the phoenix hot again for the same reason. Perhaps a similar stack concept could be used for fester to be able to use these utility abilities after summoning phoenix. So the smn is both justified for its dps by adding utilities to it, and making it a little busier by adding more weaves.