~ Introduction ~
This simulator will help you determine what sources of ultimate generation pair effectively with a decisive traited weapon, assist in identifying any under performing sources, and allow you to accurately theorycraft with ultimate generation. The editable Google Doc linked below allows you to select what sources of ultimate generation you want calculated, set individual uptimes and proc frequencies, and clearly illustrates the effect a 1H or 2H decisive traited weapon will have on specific setups.
Editable Google Doc(go to sheet 16)TL;DR
Decisive traited weapon(s) only works with sources of ultimate that tick frequently (even if for a small amount). Decisive gives a x% chance to gain a single ultimate on every instance of ultimate gain. As such it pairs best with Tava's Favor and Minor Heroism which tick every 1sec and 1.5sec respectively (however even in this best case scenario it still only increases ultimate gain by 8%). It does NOT work efficiently with Bloodspawn, WW Hide or any form of class passive or skill that generates ultimate.
~ Video Guide to Simulator and Analysis ~
(same thing below in text)
~ How to Guide ~
1) Open up the simulator with
this link.
2) Values marked in red are for you to input.

3) Mark "y" or "n" to include or exclude sources from analysis. Enter appropriate up times. Where an up time is filled as "n/a" enter the frequency that source occurs in seconds.

"Instances of Ult Gain" is the most important value in determining the effectiveness of a decisive traited weapon (higher value the better).
4) Examine your results to determine if a decisive traited weapon adds significant enough ultimate generation to your build.

~ Analysis ~
Decisive has a x% chance to gain an additional ultimate every instance of ultimate gain. As such decisive works best with ultimate sources that tick frequently for small amounts (like Minor Heroism) rather than infrequently but large amounts (like Bloodspawn). Below is a cross section of different ultimate sources combinations and the resulting affect a decisive traited weapon will have.

As you can see from the above examples, decisive has a rather limited application where the results are significant enough to justify. Even with 5 sources of ultimate generation a legendary 2H decisive weapon will still only add 1.2 ultimate per second. Whether it is right for your build or not requires you to experiment with the simulator and input your exact build.
~ Conclusion ~
Hope that helped, let me know if you've got any questions or feedback. I deliberately didn't include Asylum 2H into the spreadsheet as its proc conditions didn't really fit with the layout. If you wanted to add it in, simply lower the value of 'Combat Frenzy' to compensate for the additional ultimate you would otherwise get from a kill.
Laters,
Tay