I feel like role emphasis was what helped the design of the 4e classes be more focused and more solid. It didn't need to be called out in the class description, but knowing what you're building for is way better than trying to cram every single idea that ever graced a class of the same name (looking at you, Monk...).
Eh... I don't think the hit die really do all that Healing Surges could do. Just the concept of a hard cap on daily HP is pretty much gone with spells and potions just handing out free HP with no expenses from the target. There was a lot of design space that was used by healing surges, like how they could be taken away by traps or used to fuel certain things like rituals and magic items, or how your number of surge could be reduced by a long time condition like a Disease or a Curse.
They could have balanced them out better through the cost to cast them, and probably by having them be a bit more narrower in usage so there's a bit more of an opportunity cost to pick one. I'm not going to redesign the whole thing here but I'm sure there was something to be done here.