I'm not against strong Bottleneck promotions, but even the name implies that they shouldn't work in open terrain. In terrain like forest, hill (or later on mountains, of course), small units can be very powerful, especially in defense. That might even be an important reason why these terrains favor the defender so much in real life - you can decrease troop density without the defenders getting that much weaker. But doing something like that in an open field? That's suicide.Given that they are about all that's been employed lately, they are not abnormal by any means.
Besides, not all is 'like them'. If you take a squad of swords up against a battalion of them, you're pretty likely to get stomped. The power difference is extreme already. If we want to reduce the promotions that get x% combat mod per step difference between them and the other unit, then that's fine - I intended to make them a bit strong at first to make sure they got used and that commenting players would become familiar with them as a result. They could be nerfed a bit and still be balanced and would probably make it more 'immersion friendly'. Very few, truly VERY few, lesser group sizes have any kind of chance against a similar type of force, at least without the promotions to help take advantage of the differences and curtail the negative of being lesser in some measure.
At the moment I think it's +10%/category of difference. +5%/category of difference would probably achieve the results sought without making the promos useless.
I think the small units already get additional stealth (at least if you play with the other CM options), so that might be fine already, and balancing all the partial combinations of CM would be not only very hard, but probably futile in the end - so different advantages if you play without the stealth option (Without Warning IIRC) wouldn't be necessary, I think. That would address my proposal of additional First Strikes.
Edit: The Swarm promotions OTOH would (at least in real life) be the most powerful in open terrain, of course.