The conditions you laid out are extremely restrictive:
- Full area of attack special skill
- Fast mana speed
- Four or five star hero
- Regular, which I’ll interpret as, ‘available from training camp 20’
A hero doing all of those things would probably be very powerful and useful. Which is why so few heroes check all of those boxes. Most heroes who do a number of those things fail to meet some other criteria.
There are plenty of heroes who meet 1, 3, and 4. But their mana speed is then average or slow. Examples: Isarnia, Azlar, Li Xiu.
Or you could take a hero who does 2, 3, and 4. But then they will fail to meet number 1 by being a single target sniper, or do splash damage. Examples: Lianna, Elkanen, Caedmon, any ramming pulverizer.
I could go on, but I’ll do just one more: there are a few who meet criteria 1, 2, and 3. But they are hard to obtain. Zeline and Zimkitha come to mind - as a result they are highly prized and used in the upper tier of the game.
You did get some answers: Kadilen, as you said, and Jack O’Hare. Even they have some compensatory minuses. Kadilen does not hit terribly hard, and Jack fails to meet your fourth condition.