TBH, this so-called "strategy" seems to be pretty lame.
Long before, you could defend yourself interminably by just training 1 spear over-and-over. They realized this is not normal and fixed this. And I am OK with that since was not normal.
But now, when you just can't make use of the multi-million and months of investment in a high wall, seems to be "normal". Well, it's the same thing: IT IS NOT NORMAL.
So, I really hope they fix this and move the doctors and medics out of the garrison limit and let the defenders make use of their invested wall.
You want to take down a wall? Great, bring mortars!
The Speri thing hasn't been fixed because it still works