This research based on cohort research https://boardgamearena.com/forum/viewtopic.php?t=49572
Indians! and Gatling: when do they actually help the Outlaws?

I examined several scenarios involving the first two plays of Indians! or Gatling and compared the win rates of the Sheriff’s team and the Outlaws with their overall averages: 31% and 64.1%, respectively.
Scenario A — the first two plays, regardless of who played them
I looked both at games where the first two cards were played in the first round and at the broader group where they could be played in any round.
In both groups, the Outlaw win rate was below the overall average. Specifically, when both cards were played in round one, Outlaws won 61.9% of games, while the Sheriff’s team won 30.7%.
Scenario B — both cards played by non-Outlaws
Both mass attacks come from the Sheriff, Deputy, or Renegade.
Yet this group had a substantially higher Sheriff-side win rate: 37.8%, or +6.8 percentage points compared with the baseline. The Outlaw win rate was 54.7%, or −9.4 points.
Scenario C — one card played by a non-Outlaw and one by an Outlaw
This group includes both possible orders.
The Sheriff-side win rate was 30.5%, just 0.5 percentage points below average. The Outlaw win rate was 61.7%, or 2.4 points below average.
Scenario D — both cards played by Outlaws
This was the most favorable group for Outlaws.
The Sheriff-side win rate was 27.3%, or −3.7 percentage points, while the Outlaw win rate was 65.6%, or +1.5 points.
My practical takeaway: timing matters more than simply having a mass attack available.
As an Outlaw, I would not treat Indians! or Gatling as an automatic play. I would look for a specific opportunity.
Before playing either card, ask yourself: what specific advantage am I getting from playing it now?
How many cards does the Sheriff have? How likely am I to deal actual damage rather than just trade responses? Can I follow up with another attack? How much damage or card loss will I inflict on my own teammates?
For example, Indians! can be much more valuable after the Sheriff has lost a Duel and still cannot produce a BANG!, or when the Sheriff or Deputy has an empty hand. Finishing off a dying fellow Outlaw for the three-card reward can also be worthwhile, depending on the position.
If the Sheriff has a large hand and my teammates are vulnerable, the immediate benefit is much less obvious. Simply hitting more players does not mean I am helping my team.
My rule is straightforward: identify the value of playing the card now. If that value is unclear, hold it for a better opportunity. Having a mass attack in hand is not, by itself, a reason to use it.
Indians! and Gatling: when do they actually help the Outlaws?

I examined several scenarios involving the first two plays of Indians! or Gatling and compared the win rates of the Sheriff’s team and the Outlaws with their overall averages: 31% and 64.1%, respectively.
Scenario A — the first two plays, regardless of who played them
I looked both at games where the first two cards were played in the first round and at the broader group where they could be played in any round.
In both groups, the Outlaw win rate was below the overall average. Specifically, when both cards were played in round one, Outlaws won 61.9% of games, while the Sheriff’s team won 30.7%.
Scenario B — both cards played by non-Outlaws
Both mass attacks come from the Sheriff, Deputy, or Renegade.
Yet this group had a substantially higher Sheriff-side win rate: 37.8%, or +6.8 percentage points compared with the baseline. The Outlaw win rate was 54.7%, or −9.4 points.
Scenario C — one card played by a non-Outlaw and one by an Outlaw
This group includes both possible orders.
The Sheriff-side win rate was 30.5%, just 0.5 percentage points below average. The Outlaw win rate was 61.7%, or 2.4 points below average.
Scenario D — both cards played by Outlaws
This was the most favorable group for Outlaws.
The Sheriff-side win rate was 27.3%, or −3.7 percentage points, while the Outlaw win rate was 65.6%, or +1.5 points.
My practical takeaway: timing matters more than simply having a mass attack available.
As an Outlaw, I would not treat Indians! or Gatling as an automatic play. I would look for a specific opportunity.
Before playing either card, ask yourself: what specific advantage am I getting from playing it now?
How many cards does the Sheriff have? How likely am I to deal actual damage rather than just trade responses? Can I follow up with another attack? How much damage or card loss will I inflict on my own teammates?
For example, Indians! can be much more valuable after the Sheriff has lost a Duel and still cannot produce a BANG!, or when the Sheriff or Deputy has an empty hand. Finishing off a dying fellow Outlaw for the three-card reward can also be worthwhile, depending on the position.
If the Sheriff has a large hand and my teammates are vulnerable, the immediate benefit is much less obvious. Simply hitting more players does not mean I am helping my team.
My rule is straightforward: identify the value of playing the card now. If that value is unclear, hold it for a better opportunity. Having a mass attack in hand is not, by itself, a reason to use it.