So having a lot of Screed experience with black dice rerolls plus the back-up Screed to go fishing for hit+crits, I was curious if one could use an ISD-II equipped with Leading Shots, Captain Needa, and Turbolaser Reroute Circuits to achieve a similar end result with red dice, fishing for as many 2-hits as possible. Vader is generally superior to Screed when it comes to red dice, so this seemed like an area he could shine in. Here's what I came up with:
The odds of a 2-hit coming up are 1/8 - 12.5%.
The first reroll adds (7/8 chance of needing to reroll * 1/8 chance of getting desired result in first reroll =) 10.9%, total of 23.4% chance of a dice getting the 2-hit result.
The second reroll adds (76.6% chance of not yet having the desired end result*12.5% chance of getting it =)9.6%, total of 33% chance per dice of coming out a 2-hit result per dice.
Which, with 4 red dice (and presumed 3 blue dice from using Leading Shots) gives us the following odds:
zero 2-hits: 20% of the time; (average damage = 4.53)
one 2-hit: 39.7% of the time (average damage = 2 + 3.96 = 5.96)
two 2-hits: 29.3% of the time (average damage = 4+ 3.39 = 7.39)
three 2-hits: 9.6% of the time (average damage = 6 + 2.82 = 8.82)
four 2-hits: 1.2% of the time (average damage = 8 + 2.25 = 10.25)
(non-2 hit red dice average 0.57 damage each, blue dice average 0.75)
With Needa+Turbolaser Reroute Circuits involved, you can up the number of two-hits once more (except when you get all four naturally) by flipping another dice (usually red, I would assume). Preferably you'll want to give up a blank dice for this effect (which is a net +2 damage) but sometimes you'll need to flip a single hit or an accuracy. It's difficult to map out exactly how many accuracies you would want to keep in the pool (versus spending blue ones for Leading Shots or red ones for TRCs if there are no blanks), so the assumption is that giving up a non-blank red dice is the average result of the non-blank sides, which is 0.8 (2 hits, 2 crits, 1 accuracy), resulting in a net gain of 1.2 damage. Thus the benefit of flipping is an average of (blank chance*2) + (non-blank chance*1.2).
So we need to look at the chances of a blank showing up in all of the non-quadruple 2-hits results above:
0: 68.4% chance of one or more blanks, meaning Needa+TRC flipping a 2-hit buys us an average of ((68.4%*2)+ (31.6%*1.2)) 1.37+0.38 = +1.75 damage to the 0 2-hits results
1: 57.2% chance of 1+ blanks. So ((57.2%*2)+(42.8%*1.2)) = 1.14+ 0.51 = 1.65
2: 43.7% chance of 1+ blanks. So ((43.7%*2)+(56.3%*1.2)) = 0.87 + 0.68 = 1.55
3: 25% chance of 1 blank. So ((25%*2)+(75%*1.2)) = 0.5+ 0.9 = 1.4
4: all the dice are miraculously 2-hits, so no need to use TRCs.
Okay so this gives us an end result of:
20% chance of (4.53+1.75=) 6.28 damage = +1.26 average
39.7% chance of (5.96+1.65=) 7.61 damage = +3.02 average
29.3% chance of (7.39+1.55=) 8.94 damage = +2.62 average
9.6% chance of (8.82+1.4=) 10.22 damage = +0.98 average
1.2% chance of 10.25 damage = +0.12 average
So the total average damage from an ISD-II front arc at medium range should be 8 damage using this method.
The normal average damage of an ISD-II's front arc is (8*0.75=) 6. So this is a net gain of 33.3% damage.
Whether it's worth the hassle. I leave that to you
. I can't say I recommend the second reroll rerolling
everything
but double-hits unless you've got the TRC backup available, but that requires some more probability math I'd rather leave alone for the time being. If you see any errors I made or have any comments or questions, please let me know.
Edit: Fixed an incorrect assessment of non-2-hit red dice damage. Caught an addition error as well. Average damage actually IMPROVED from my initial assessment from about a 25% gain to a 33.3% gain. That's substantial.