Cool, cool, and cool!
As always, the lore is my favorite part. I think it goes without saying that you always find a way to balance new and highly-developed ideas without making them complex to the point of boredom, and find a way to tie them into the already-existing story.
Having 2 separate attacks rose some skepticism in me because R&R's worst quality was how Razz would inturrupt Rags' AOE with his ranged attacks, but from what I understand, this is an improvement, as they attack at the same time amd independently from each other so that nothing is inturrupted.
Rising Sun is an epic name for an epic skill, but I have 2 big issues with it. The first is that the hero has to be near slain enemies to get the benefit of damage. I really get frustrated using Captain Blackthorne because I want to get as much gold as possible and move him around to try and get the Looting bonus from every enemy that I can. I would do the same with this hero knowing that I can infinitely stack damage, and end up moving them around all the time and gathering solar power instead of using abilities.
The second problem is that with abilities being recharged and how slow but strong each skill is, power usage will matter much more than base attacks (once again like R&R) which makes a damage and health passive rather UP since it won't come into play much. I would recommend taking out that bonus and focusing solely on skill recharge, making that category more powerful and further emphasizing a playstyle based around using extremely powerful skills to wipe out the majority of enemies.
Ability visuals have never been so good before the creation of Wind Sun. I would love to see that in a video game so badly.
I was first expecting this skill to be a hurricane sent down the lane, much like the Archmage's twister. Instead, it's a magical hurricane that sticks to one enemy. It's a neat idea since it keeps the damage focused on a target, but I can't help but feel that if it traveled on its own and caused unbridled destruction, it would match the epic, powerful qualities set up by the animation of summoning the winds that you've described. Maybe it could slow down enemies so that they would stay in the AOE for longer, keeping part of the idea of keeping enemies in the AOE, but without tracking a single target.
Earth Sun is a really awesome skill. It does more damage based on how much initial damage it does, which benefits players who use these heavy, risky skills very well. There are no negative critiques that I can give to this.
The final elemental sun skill reminds me of the first: It deals the most damage to a single target, but also causes harm to nearby enemies. It serves it's purpose and looks really cool, and since the output of the skill doesn't clash with how the power is summoned, I also don't have anything bad to say about it.
Although cool, the hero spell is a little overkill. Only Dark Pact has that long of a cooldown, and it lasts for 30 seconds. 840 AOE damage is too much anyways, as Twilight Evokers and Scourgers don't have as much hp even on Veteran. Something between this damage and Eridan's hero spell which can barely kill a full health Harrasser would make it less rarely used while still having the huge impact that you want it to have. I really like the continuity between uses of the spell; it makes it much more interactive and thus equally more fun to use.
A very, very solid hero.