Increase the healing reduction to -77%
Increase the activation rate to 7% per refine
Remove the + healing per refine, replace with +attack speed and -mana cost per refine (I'd say 3% aspd and 1% mana cost reduction per)
Optional: It might be cool to make it have a set effect with Royal Crest. Visually complimentary and effectively synergized. I'd say resistance as set bonus to warrant keeping the shield equipped, but could just double down on mana cost reduction and/or healing.
Yes, this is my favorite item and my build. I'd prefer it just be a skill/part of our innate kit, but if I can effectively enjoy my bonk healing through the Cerulean Scepter.... 🙂