I hear you. I'm still early in the grand campaign for US, trying to tweak everything now so i don't end up on day 25 with a totally unrealistic result.
Some tweaks were to adjust the victory locations:
1) put them in places you think would be advantageous for the attacker to spread out too. They'll go for those places. put them in places where you think a good flanking attack might occur.
2) keep them away from the edges of the map. AI doesn't like traveling across the map to an edge on the other side. So move the VL's closer to the center of the map, which also makes defending them harder. The closer the VL is to where the AI units are, the more likely they'll be aggressive in taking this next VL.
3) if you also limit the # of VLs (although some argue for more VL's), it's that much harder to hang on to them. For example, in south eiffel, i moved the exit VL's to schonberg and losheim closer to the crossroads. I pushed the "to andler" VL, to the forest just west of the crossroads. Now defending is a little more aggressive towards the crossroads, and if they catch all the VLs, youre going to get disbanded.
There is also a way to adjust how dense the the AI forces start off in a map by adjusting the map .txt file in the maps folder. The 6th row of text tells you how dense the AI should be. 0=spread out. 1 = mixed. 2 = dense. I don't know which maps you are playing, but all the early ones in the grand campaign are already spread out, that doesn't help me.