Actually, this buff is not for making the card better compared to the other shields (I'm think too this is a very good shield), but there's a thing what I want to propound.
"Why don't Bone Wall stacks?"
The Bone Wall is a shield, what gives you 7 shield counter, every counter negates 1 attack. When Deflagged, it's lose 1 counter, so that means the Bone Wall is not 1 shield, it's 7 shield counter and an effect in them. But with this logic, when this card gives you 7 counter, I don't get why you lose every shield, when you build a new wall. Despite the other shields, you don't have to ruin down the older shield to build up the new one, you can build the new ON the old, as like the old can get a counter by using the bones and skulls of the creatures.
Dimensional shield is the best shield in-game, but there's not really other shield to compare with (Dissipation is one too, but I think it's the second best, so there's no real improvement), but you can stack Dim. shield optimally without inner help. You see, when the counter becomes 0 and make an other without taking ANY damage. But if there's a Bone wall on field with 3 counter, an other in your hand and the opponent have 5 creature, you don't really have a good choice...
Thanks for reading!