Your characters don't set up traps? Weird.
You cannot set a crossbow and a tripwire to shoot in whatever direction an enemy comes from. Cordon is roughly equal to two crossbow shots in damage, except that it hits in any direction, including up. If you're allowing PCs to somehow set a trap to do the same, then your sense of what is balanced in comparison to setting a trap is completely bonkers, because you're letting traps do nonsense.
If you're letting them set that trap in 6 seconds/as an action, well, don't even try to talk to me about balance.
Anyways, by 5th level, there's typically a few extra crossbows, and often some manner of storage solution. Moreover, you don't need 4 crossbows to beat Cordon of Arrows. You seem to overlook that any creature would only be subject to one arrow save per round. It's the first time a creature enters or ends its turn in the cordon that it has to save. Another reason the spell is junk. It's at best a d6 DOT with a save to negate each round, which as I said, is nuisance level.
I haven't overlooked anything, you just aren't making compelling arguments, here.
Hybrid spells, particularly damage dealing ones, need to be stronger on a level by level basis, otherwise we get the . Look at Prayer of Healing and Find Steed. That should be the benchmark. Otherwise you get situations like the Eldritch Knight, where the damage dealing ones are pointless compared to what you could already do with your martial skills.
The Eldritch Knight isn't even a good case to discuss when talking about ranger spells, because the EK has no access to similar spells. No smites, or smite style spells, closest things is Shadow Blade and the melee weapon cantrips.
Still, the EK doesn't do bad, with those spells they do have.
I made a sword and shield, Dueling FS, level 8 EK with equal int and str, which is how I mostly see them played, and looking at my attacks, I've got 2 attacks at 1d8+5 with a longsword or rapier. I could have gone Dex with a rapier instead, or GWF, but this is a good average character for comparison sake, and closer to what I have in my party in my friend's campaign right now.
I also took War Caster and Spell Sniper at 4 and 6, waiting until 8 to boost my stats at all. It'll be 12 before my strength hits 18, but since I don't build max stat characters in real games, I won't do so here.
Comparing that to his damaging spells, we've got:
Absorb Elements. I'd probably sacrifice a little Int for more Con if I were to play this guy, and use this when Shield doesn't apply. I won't put the extra damage in the examples, because it's too depending on the enemy one is fighting, but when fighting things that do elemental damage, it's really nice to have.
Cantrip+ bonus action attack - 2d8+5 and then 1d8+5 as a BA. With Shadowblade on, this increases by 1d8 per attack. Pretty good, especially if you have Advantage to equal out not making more attacks. That's what I'd expect for spending a bonus action on a class that doesn't use it's bonus actions for class features.
Just Attacking: 1d8+5 twice. 2d8+5 twice with Shadowblade.
Ranged damage spells have to compare to rather weak ranged martial options on this build, which isn't necessarily fair, but it does point toward one of the many benefits of this subclass. That is, you can be just as good at range, without being a dex build.
So, level one I picked up Ice Knife. It isn't the most powerful optimized choice, but it's fun as hell and frankly I don't run into damage resistance all that often, as our games tend to battle humanoids more than anything else. Still, the fiends can sometimes be resistant to cold, so Magic Missile is probably the more practical pick.
Hand Axes: 1d6+3 twice, possibly a third as a bonus action. With Shadowblade one of those attacks could be 2d8+3 instead, but that precludes the bonus action throw. Best round possible is two hits, one with shadowblade and one with an axe, for 2d8+3 and 1d6+3, with rather short range.
Chill Touch, and bonus action thrown attack, with shield equipped (it makes sense in my games, because enemies do heal eachother): 2d8 and then 1d6+5 or 2d8 and then 2d8+5 with shadowblade. Not really impressive compared to what another subclass can do with an archer build, but perfectly respectable for a non range focused character.
Lightning Lure and a bonus action melee attack: 3d8 and then 1d8+5 (2d8+5 with shadowblade). Pretty good when the situation calls for it.
Ice Knife: Spell Sniper, range 120 ft, 1d10 initial damage and a blast secondary that deals 2d6 in a 5ft radius. Let's assume you use this when you have at least 2 creatures next to eachother, and you upcast it. Best possible round is 1d10+3d6 to one target, and 3d6 to another. Obviously it's better the more creatures can be hit with it. (also EKs really benefit from the sorcerer mc feat)
Scorching Ray: 2d6 three times, used as needed in terms of targetting, range of 240 ft. Best possible round is 6d6. An archer would be more accurate due to the fighting style and 18 dex, and if we assume a BM they'd likely be spending 2 dice to make it 2d8+4 twice with some secondary effect.
I mean, you're acting like there is some huge gap here, but there isn't. The BM can dish out more consistent damage while their dice last, but they have far less utility, and little in the way of extra defense, and if they want to be good at melee and range they have to go Dex, which is fine if the player wanted a dex character anyway, but not if they wanted a heavily armored himbo or whatever.
Obviously the EK could use something better at level 7, but honestly just making it any spell reather than only cantrips that allow a bonus action attack would help, and the biggest let down of the class is that this feature doesn't allow synergy with things that add to an attack action. It's casting is fine as long as your adventuring days aren't long enough that you run out of slots, and you take Warcaster to allow easier casting and more reliable keeping of concentration.
The case is even better for the Ranger, who is getting spells that add to their attacks rather than replacing them, and generally do useful secondary effects as well. Cordon of Arrows is perhaps their least impressive combat spell that they don't share with other classes, but since I consider it the same as a spell that just adds 1d6 to your next four attacks but doesn't require concentration, it's fine. Worth preparing if Rangers were prepared casters, which is the only real dissapointment of ranger casting; the limited number of known spells.
I mean, look, if I'd been desinging the game, I'd have made all casters gains access to spell levels at the same rate, and given lesser casters slower progression of spells known/prepared and spell slots, and you'd just be picking spells of X level or lower for more of your career rather than waiting until level 9 to get 3rd level spells, so that we could balance all spells of a given level the same, regardless of intended class, but that ship has sailed, and what we got works just fine.
visual cover and that s*** stings!) would probably make more sense for the game.
