Auto-translated
The damage dealt is minimal. And it's easy to catch and counter with other spells. I don't think there will be a moment during the battle when it's appropriate to use the devastating beam. There will be high Darkness, there will be good spells, it's better to use mass slow/berserk, etc....
It depends. Faizu immediately learns Cursed Ground. Mass slow is also not difficult to learn, and it's still easier than for other mages. Besides, the mage has the most ranged units, so the devastating beam is a good fit, plus it has an additional effect. The start will be difficult, yes. But playing with other heroes gets boring, to be honest.

