Here's your dose of early morning
Fire Thokcha beats Coruscanti offhand for Twashtars by a
smidgen according to current spreadsheets (assuming Exenterator usage)
Unless: (1.) Berserk is up or attack is otherwise very high relative to your target.
(2.) fSTR is capped otherwise (Boost-STR)
It's so close though that ODSD will barely have to do anything to beat Thokcha for an offhand. ODSD needs to average out at like +2dps at the most to pull ahead always 8V
Incoming Fuzzy Math
Assuming it's OQD, and your normal average damage from a Coru hit is D, and crit rate is capped - making a lot of the assumptions I've made before but it's not too important to worry about:
Dps from Coruscanti = (1.38(D+0.3D))/(1.59) = 1.12 D
Let P be the proc rate of Coruscanti's ODSD
then we can estimate that if it's some P % of OQD, then to beat X dps from Thokcha, we need
P >= (1.15(X+1.12D)-1.3D)/(3.9D)
so if D = 60 and X = 5
then the proc rate only needs to be greater than 2.1% to win.
If D = 60 and X = 10 (as in we need 10 dps to beat thokcha - which is pretty unreasonable seeing as there's usually 0.1-2 difference between them depending on how I set the mob stats)
then we need a 4.6% proc rate to win.
tl;dr Mathematically, it won't take much ODSD to beat Thokcha for an offhand.
-----------------------------------------------------
If you're using
Coruscanti, Charis Feather appears to beat out Potestas Bomblet (but Bomblet is superior for Thokcha).