Drizzt was never really treated as a Ranger in the novels. Rangers have spellcasting, and the only spells he ever used were basically his racial ones. He just had the ability to track and live out of doors.
In the NPC guides, they flat out give him weapon spec and the ability to outright kill lower level creatures on a hit. Nothing is made of his anti-giant ability (during 1E and 2E) or favored enemies (during 3E).
His training was basically drow fighter with stealth skills. That's it. He was just incredibly high level (16th or so), so he dominated the rest of whatever party he was with. Contrast Wulfgar starting at 6th level in the first novel, and Bruenor being 10th, Regis being 6th, and Cattie=Brie being 4th.
He was never an optimized character, except he was so much higher level then everyone else. That was the solution for 'drow are powerful' in FR...make them higher level then all their enemies, that explains everything.
Technically speaking, with a 19 str and 18 Con, Wulfgar at 11th level with 2 attacks from his hammer would have utterly obliterated the 1e Drizzt in 2-3 rounds. Drizzt had a 15 str and no damage bonus except weapon spec, and only got decent weapons in later novels (he was using MAYBE +1 weapons in the 1st book, and acquired a frost brand scimitar during it).
TWF didn't become an iconic part of the ranger until 2E, when it became part of the core fighting style in the PH. However, 2wf was available to anyone with high enough Dex, no training required.
In short, the gaming stats for Drizzt didn't match his deadliness in the novels unless you introduce a bunch of parry mechanics and criticals...and then take into account the fact he was 5-10 levels higher then everyone else.
You're right, but I was saying, that due to his popularity and the fact that Salvatore couldn't go three pages without calling him a ranger, is why the dual wielding rules were included