Yes, this worked very well in Wargame and CoH because of the small scale and tactical focus of the gameplay. Ashes is much larger in scale and seems to be more focused on strategic gameplay.
I do think this would be a nice mechanic, but I'll copy and paste a paragraph from that massive reply I made to the August FAQ topic lol
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You have to keep in mind, that if 500 brutes attack 500 brutes, it's not a 500 v 500 battle. It's only the front lines units firing while the rest mill around doing nothing. This is only changed by "running through", to forcibly engage more units at the same time. In which case, the leading units would slowly get chewed up, and the result would be more or less be an equal exchange by both sides. The only way to change this outcome with homogeneous units is positioning. One side would have to outmaneuver the other so that it somehow attacks with a greater concentration of fire power in a certain area (imagine a line of 20 brutes wide attack a column of brutes 10 wide. The 20 unit wide would win since they could bring more damage to bear quicker).
This is the reason why "pro" players in FAF always tech relatively early. Because a t2 unit has more health, more range, and does more damage. Essentially it is more "condensed" firepower, allowing you to bring more damage to bear at once (since you could only get so many t1 tanks shooting at once). "
So... The point here is that even with different armor facing types, run bys (which is till a problem my opinion as they are very easy to do) will still more or less result in an equal exchange by homogeneous units. Obviously when you start considering a mixed meta unit, this starts to change, but the result would be the same with mixed metas of the same composition. Directional armor would not change this because, well, both armies would get roughly equal number of flank and rear shots at each other.
Also, the way meta units create formations rather limits the idea of tactical flanking. What I mean is that units are not fast enough to warrant any fancy tactics such as splitting off some of your meta unit to skirt around the enemy meta unit you are engaging. The only kind of flanking that works is more of a "strategic flanking", where you entirely cut off an area, and then end up attacking an enemy army with 2 separate armies of your own. However, I find many of the maps in Ashes are very "corridor like", and so this type of flanking is quite uncommon.
So this just leaves us with what we have - meta units blasting away at each other from the front, and most of the time i'm just running through the enemy meta units to save time (since I know my meta unit wins regardless, I might as well capture the power node while fighting and then move on, as opposed to killing the enemy, then capturing, then moving on).
These issues above rather limit how unique directional armor would be.
I think that in order for directional armor to have an a serious interesting affect on the game the above will need to be changed somehow.. be it either with having some faster units, have units behave differently in formation/out of formation, unit speed, better map design with less corridors etc.
But as I have been saying, I'll need to see more of the game before I could write anything about how actually fix this in game.
I hope this makes sense, and doesn't sound like some crazy rant haha. Let me know!