And it can't be rebalanced within realistic terms either. It has gotten a lot of QoL buffs lately and it's good enough for casual play now. ... Similar to a unit like the B4, it will just never be competitive due to its nature.
B4 and AVRE can be used competitively, maybe not in 1v1 and not in super top play, but both units are in meta somewhat. But sturm as you point out is a casual unit which realistically is useless against players who know how the game works.
And there is nothing about "relic scope", I belive that there is no more "scope".
I honestly dont know how and on which conditions balance team works, but sturmtiger was nerfed across the board, AVRE wasnt, even considering the fact that AVRE was always better then sturm in its role.
If balance team wanted Sturm to be more forgining and not deleating armies from the game by 1 click, thats why they left him with this AOE profile, then it also should have been applyed to AVRE.