Well, that's all true, but you need to consider that the stone has 800 HP. Will every unit (or even a group of units) be able to take it down right away?

There are many things you can take into account. In fact, a "dead end" where one hero stands, and another hero in armor with amazing health, regeneration, and a bunch of healing and immortality potions completely blocks, for example, a poisoner or a flamethrower, can be considered a "dead end." THIS OBSTACLE in the form of a hero is not much different from a stone with 800 health; moreover, it will also attack back :) unlike the stone.

also... It's still an interesting spell, but it's overpowered in tournaments... And regarding

In principle, you can say this about any of the existing spells :) In an offline tournament, there cannot be such a thing as an "overpowered" spell. If desired, any of the participants can use it at their discretion. In an online tournament, where one participant may have this spell and the other may not, it is appropriate to discuss this issue, meaning regarding the "overpowered" nature of the spell. Moreover, it is a non-standard spell and is not in the official version of the game.

what to do... But I would like to hear your opinion (preferably from all our Grandmasters of 4 Heroes and, of course, from General Zeta)...

In principle, this opinion has already been expressed, including by General ZeT. A magical "dead end" is not prohibited.
A generated "dead end," the items that make it up, cannot be destroyed by the opponent in any way - this is prohibited.
This is quite reasonable, at least for offline tournaments.