Math time!
Ranger 11 (Beast Master), TWF, shortswords x2, Hunter's Mark
+9 vs. AC 16 (5 dex, 4 prof), plus Panther +8 vs. AC 16 (bite damage 1d6 + 6), Bestial Fury
2 * (.65 (3.5 + 3.5 + 5) + .05 (7 + 7 + 5))
+ 2 * (.6 (3.5 + 6) + .05 (7 + 6))
= 17.5 + 12.7
= 30.2
Ranger 11 (Hunter), TWF, shortswords x2, Hunter's Mark, Colossus Slayer, +9 vs. AC 16 (5 dex, 4 prof)
3 * (.65 (3.5 + 3.5 + 5) + .05 (7 + 7 + 5))
+ (1 - .35^2)4.5 + (1 - .95^2)9
= 26.25 + (3.949 + 0.878)
= 31.077
So, at least for Lv. 11, the same level the Fighter gets his third attack, the Ranger (both builds) actually isn't looking too bad DPR-wise.
Comparing to two types of Fighters at this same level:
Fighter 11 (Champion), Dueling, rapier, +9 vs. AC 16 (5 dex, 4 prof)
3 * (.6 (4.5 + 7) + .1 (9 + 7))
= 25.5
Fighter 11 (Champion), Great Weapon, greatsword, GWM (no -5/+10 trade), +9 vs. AC 16 (5 STR, 4 prof)
3 * (.6 (8.33 + 5) + .1 (16.67 + 5))
+ (1 - .9^3)10.165
= 30.495 + 2.755
= 33.25
I picked Duelist for the "finesse" Fighter because it's strictly better than TWF for a pure Fighter at Lv. 11 with 3 attacks. The Duelist Fighter is well behind both Rangers.
Even the much-ballyhooed Great Weapon Master isn't terribly far ahead DPR-wise. (He can technically get 37.069 DPR if he does the -5/+10 trade, but the variance becomes so ridiculous there that it's really not worth doing that.)
Where the Fighter DOES maintain a HUGE advantage, however, is burst damage via Action Surge. Rangers simply don't have an equivalent to that, or even to something like the Paladin's Smites, for that matter.