Brave Frontier Infographic: Damage Percent Increase
1st pic - Our main unit who does 1 hit per turn(3 star Gallant)
2nd pic - 1st squad, no bonus damage that could affect our unit whatsoever.
3rd pic - Original Damage (no leader, element, or any other bonus)
4th pic - Elemental Bonus (50% damage increase based on the previous damage output)
5th pic - Elemental Negation (50% damage reduction based on the original damage output)
-From this point on, the damage increase the unit got is around 50% based on elements.
6th pic - Squad leader: FG Vargas (50% damage increased from leader, 50% from Element)
-It's notable from this pic that the damage increase stacks AND accumulates. Original damage is around 800, +50% which is 400 (Leader bonus) = 1200 + 50% which is 600 (Elemental Bonus) resulting in around 1.8k damage.
7th pic - Last squad (50% leader bonus, 50% friendship bonus, Also bringing one ore to be used for additional 50%)
8th pic - 3 bonus damage increase this time (50% Leader, 50% Friend, 50% Element)
-As you can see, the damage still stacks and accumulates but it somehow diminished. Based on the 6th pic, I was expecting that the damage would be 1.8k + 50% (Friend bonus), which is 2.7k, but ended up 200 short.
9th pic - 3 bonus damage still (50% Leader, 50% Friend, 50% Ore)
-Far off from the 8th pic (2.5k), the damage here is 500 short from what I expected.
10th pic - 4 bonus damage increase (50% Leader, 50% Friend, 50% Ore, 50% Element)
-Damage still stacks, but does not exactly accumulate completely. got around 3.3k here. If it accumulated completely, I would be expecting around 4 - 4.1k damage (2.7k + 50%), but ended up 800 short.
I don't know if you can take into account that there's a slight chance that the units I'm hitting may have a different level, though the damage change shouldn't be that significant. All hits done here are normal, none are critical.
My conclusion is that the lesser the multipliers are, the more effective the stacking is. The more multipliers that we have, the more diminished is the stacking. Also, it seems that Elemental countering is more effective than just plainly using ores and leadership bonus, it may have a higher percentage of increase, 50% is just a guess based on the original damage output.
Add me if you have GK Will / G Atro / FG Vargas / FG Lava, I'm still working on my mono fire and mono light units but I use either HK Atro or FG Vargas as leaders from time to time. My player ID btw is 99923562, have fun guys :D