Currently archer missile height seems to be capped quite low, singers seem to be roughly the same but a bit higher. Javelins height seems to be inifinte judging from the times I've seen soldiers launch them to the moon. I get the reason for this is probably realism, but it can be very irritating.

In pitched field battles, if you are firing from high to low elevantion with spears in front of archers for example, the archers just shoot into the backs of spears because they use a really low trajectory.

That though is a comparatively minor issue compared with sieges. missile units are significantly nerfed in sieges as they seem to be completely unable to fire over buildings due to the trajectory height limit, except for javelins. If you are attacking, there is usually a sweet spot where you can sometimes fire over palisades, but if you want to fire missiles inside the city, you need direct LOS. This makes archers and singers almost useless defending unless you have stone walls for them to sit on and makes them significantly less useful when attacking too requiring lots of micro to make them effective.

Historically, missile units would have been at their most powerful in sieges, think archers and slingers sniping at soldiers as they march down streets from houses and rooftops, so the nerfing of missiles in sieges is not historical and it is also not fun for the player and it is not balanced (heavy infantry are already extremely strong in this mod and don't need more help to make them even stronger in sieges where cav is already a non-factor!). Please would the devs consider tweaking missile heights and trajectories to be more like vanilla so archers at least can fire over buildings and troops will favour trajectories which don't cause as much friendly fire in the field.