Zardnaar
Legend
I am pretty sure it is not optimal for the overwhelming majority of levels. I've seen numerous charts of the damage comparison, and GFB/BB beat TWF for almost all the levels, due to scaling of the cantrips damage. I guess I need to dig one of those charts up, since you're the second person to make this claim.
White room yes but.....
1. GFB misses, dual wielding gets another attack.
2. Has the rogue splashed the fighter level?
3. Most games likely are lower level.
GFB doesn't win single target until level 9 or so.
Online only 10% of games go over level 10.
Throw in misses and dual wielding looks pretty good.
Pre Tasha's anyway.
Level 1-4 it's roughly break even but you double chance to sneak attack.
GFB lvl 5 wins on paper but yeah still double chance to sneak attack.
If you splash that fighter level roughly even.
Level 9+ gfb starts looking better.
Post Tasha using new rule it's a blow out imho to GFB.