Graftblood and Hiveborn encounters: what am I missing here?

I am in L45 zones (second part of the plot), and I see no increase in graftblood income - it still from 10 to 50, depending on luck mostly. But practically every encounter gives me wombgift now, sometimes even two, and right now it's 93 graftblood for activating it.

So, obviously, I need at least 2 (but 3 is much more often) encounters to activate one wombgift. While I receive about three wombgifts in the same time. And I suppose, at the end of the plot levels it will be about 120-130 graftblood per wombgift, with the same average 35 income, so rate of activation will be 1:4 or even 1:5.

Is it expected? Must I discard all wombgifts, except highest levels, and hope to activate at least some of them? Or did I miss something here?

Oh, and side question: what use of all this walls and magenta points during defence? It seems, all my oh-so-important ability to disrupt walls and activate these points does nothing? Or I missed something here too?

tbh in campaign u get let max60 blood(dunno if hives spawn there think not but they give always most)
in maps u start getting 150+ i think then yellow maps give more then at maps u get like 500+ each map u do

Good to hear, as I started to fear that system is broken.

Thank you! :)