==> provides low to moderate support, especially to dispatch targets with almost no hp, or light armor targets with immediate/high threats.
==> their real value are only shown when:
1) high grounds. One step higher provides more accuracy than one step closer.
2) terrains that requires enemy to take extra steps to get to you.
3) swamp terrain which greatly slows down enemy.
4) unarmored or light armor enemies, and enemies without shield.
I initially started with zero ranged units after reading your post (I looked over the ‘net for game advice before I started to play), as well as Duungarm’s excellent Steel Cohort Guide on Steam. Since I do not like ranged units in general whether in TBS or RPG (too fragile mainly and thus requires too much babysitting). After intensive playtesting, however, I have changed my mind and incorporate them in small numbers (two, to be precise).
Now you’ve provided a good beginner’s list of when and why ranged units are useful, but your list is hardly exhaustive. Personally, the main reason is to counter ranged units. On the one hand, I run quite a few melees with low armor and/or no shield (six, to be exact, two Nimble Swordmaster riposte bots, two Nimble Captains, and two offensive melees who will ideally take out their two handers ASAP), so they will get ripped if they get focus fired. So to protect them, I have to hunt out the enemy archers first. On the other hand, as I’ve complained elsewhere, hit and run (mostly run) archers are annoying, especially during nights or on bad terrain, so I need my own ranged to deal with them quickly in mop up situations.
In addition, massed Perfect Focus archer batteries can be frightening if correctly used, even against heavy Orc formations. Archers with Perfect Focus can easily get four Aimed Shots off per turn with captain support, and if you properly pin your opponents with melee roadblocks (especially Nimble characters that fear no melee and can solo an entire melee army), then you can sit back and eliminate your opponents in a few turns. Even if you bring just two archers like I do, the initial volleys can soften up the enemy to the degree where your heavy melees can frequently one or two shot wounded units.