It's kinda funny that drizzt do urden, probably one of the most popular characters in dnd, is a dual-wield ranger. But you can not actually replicate his fighting style effectively
It's because he's from older editions that have worked differently We don't actually have his class makeup for 5e yet, but I imagine it'll be a fighter/ranger mix, heavy on the fighter, like it was in 3.5.
5e and 3.5 actually share this issue, dual-wielding is not good unless you use feats and styles to specialise into it, but 5e has it worse because now you have to choose between feats and ASI, unlike earlier editions.
A big balance issue is rogues vs fighters. Attacking with your off-hand results in a roughly constant additional ~35% damage for rogues (depending on exact level, Dex, weapon, etc), but it results in a range of 45% to only 5%, as you grow in level (sharp drop at lvl 5 when you get Extra Attack), buff to fighters' damage. Great at low levels, but terrible at moderate-to-high levels.
While I can't back up your numbers the overall statement is correct, having played a dual-wielding fighter/rogue myself.
