I'm going to assume that for the sake of this discussion we are not including multi-classing, in which case Ranger is absolutely beastly btw.
As previously stated Rangers typically do better against hordes, but there are several ways to play them. Math time!(it actually really bothers me that you didn't show your math, so i will)
As per your original with 5 turns against a training dummy, I am assuming the dummy attacks once per turn.
First the single-target build;
Dual Rapiers, Two weapon Fighting, Giant Killer, +5 dex, Multiattack Defense, Evasion.
4 attacks per turn (2 as action, 1 as bonus, 1 as reaction)
each attack; 1d8(4.5)+1d6(3.5)+5 =(13),*4=52
over 5 rounds is 260
you can eek out another 3.5 and advantage with a level 5 Ensnaring strike, assuming they fail their str save every turn that looks like;
1d8+5*4=38+5d6=55.5
5 rounds=277.5
there really aren't "tricks" so I can see why this looks low, but it is definitely not unplayable.
This also has a lot of defense bonuses vs the fighter/Paladin. Evasion and Multiattack defense are awesome when going toe to toe with a dragon as you prolly take 0 of the breath attack and the extra 4 to your ac is massive when they hit that hard. Ranger also gets absorb elements as a reaction which is super useful against most big bads.
Next let's look at the Horde Breaker style Ranger, vs 3, 5, and 9 dummies again making one attack a turn against him each(1d8+4 for this example);
Dual Rapiers, Two Weapon Fighting, Horde Breaker, Multiattack Defense(because running is for pansies), Whirlwind attack and stand against the tide.
Concentrating on a 5th level ensnaring strike on one enemy, using Whirlwind attack, Stand against the Tide and Horde Breaker every turn;(1 attack per enemy, 1d8+4 for stand against, 1 attack for horde breaker, 1 attack for bonus action)
3 Enemies;
((1d8+5)*5)+(1d8+4)+5d6=73.5 per round
5 rounds=367.5
For every enemy you add 1 attack per round, so you add 9.5 dpr and 47.5 over the 5 rounds.
so 5 enemies;
92.5 per round
462.5 in 5 rounds
9 Enemies;
130.5 per round
652.5 in 5 rounds.
The highest is only 2.5 shy of your highest score. That seems pretty on-par to me.
Also the Ranger isn't using any of his "Tricks" one 5th level spell slot that is situational honestly, so if you want to throw a dagger and do a conjure volley you still have plenty of slots. as far as defense goes an ac of 18 isn't awful and by this point in the game most enemies to be concerned with have multiattack to do 1/2-2/3-5/6 of their damage, all of those will be against a 22, easily high enough to be missed a lot.
Now if you want some high numbers ask me about multiclassing.
