hi, damage depends of yours and enemie power and status, if your ninja causes 11k ninjutsu damage but the oponent ninjutsu resistence is 15k you will causes less damage, but if your critic rate was higher have a chance of the damage was higher than the 11k, but everthing depends of elementar resistence of your enemies and your elementar damage

-Do different skills have a hidden multiplier for damage or are skills with same description always identical in damage?

would like to know this too

-For example if two characters with same stats have a skill which causes ninjutsu damage to 3 opponents with no special combo or other factors described, is their average damage same?

Its probably same base damage (or RNG from base damage) and then reduced by resistance, defense etc

-Some skills will say stuff like "Causes heavy ninjutsu damage" so that means it's better than normal ninjutsu technique?

- Do characters have built-in factors such as someone has more ninjutsu than others when you recruit them? Do some gain more ninjutsu than others as they level? Is their damage etc. always in relation to the shown stats or are there hidden multipliers for different characters that affect these outcomes?

There are different hidden tiers of ninjas (blue, purple, yellow, red), im guessing they have different stat gains but it does'nt seem to make much difference in practice

- How much more damage will a skill with ninjutsu + taijutsu cause compared to only ninjutsu or only taijutsu? Assuming of course the character has same amount of both

I saw a thread about the damage formula here on forum and it says that outgoing damage = 50% NIN + 50% TAI for such ninjas, but in practice ninjas with hybrid damage seem to do much more damage than ninjas with pure damage, so it might not be true

- How does combo affect damage? Say I have a skill "Cause ninjutsu damage to 1 target" and "Cause ninjutsu damage to 1 target and 5 combo" will the latter for example cause 5x the damage on average? Or will it do 5 hits with only 20% damage each?

If you check the damage numbers in game it shows that each hit does a fraction of the total damage

- Will damage go up as I get more combo? Will the 20th strike be more powerful than the first?

Definitely not, they are all same

There is a kakashi NPC in south konoha, you can fight him to test different teams and measure damage

Hello!

The game really does a poor job explaining a lot of things. When you're reading Ninja's skills I recommend that you go to a website called Konoha Proxy. This website essentially tells you all the info about ninjas skills and abilities that the game doesn't.

If you're looking for in depth on how stats work:

Initiative = if your ninja has higher initiative than your enemy same position(move) ninja then your ninja will go first (I am saying this because you gotta know the meaning of positions in team, if your Pos2 ninja has 10000 initiative it will still go after enemy Pos1 ninja who has 5000 initiative)

Initiative is very tricky but most of the time you will benefit from being faster than your enemy (makes for interrupting, immobiling , chaosing your enemy and dealing damage first)

Your auto-barrier depends on your entire team initiative (so pos1+pos2+pos3+pos4 initiative = overall initiative which is compared vs your enemy and who has higher overall initiative will win the barrier)

There is also an interesting rule that your Position 2 ninja will be faster than your/enemies Position 1 if it has 10000 MORE initiative (example: Position 2= 15000 , Position 1= 4999 , Pos2 goes before Pos1)

(This rule also applies for Pos3>Pos2 and Pos4>Pos3, the rule for Pos3>Pos1 = 20000 more initiative but that is impossible for us to achieve)

Critical = Increases %chance of Critical, decreases the %chances of receiving a critical from your enemy (this all depends on your own ninja critical vs your enemy ninja critical)

This stats is very important for all ninjas also, especially for your main damage dealer which is mostly Pos1 ninja as it will make him crit much more often and we all know critical damage is much higher than normal one.

Critical damage has nothing to do with "Critical" stats, it depends on Injury which we will talk about next!

Injury = Increases CRITICAL DAMAGE, decreases the critical damage taken from your enemy. (same as critical also depends on your ninja injury vs enemy ninja injury)

You see the massive criticals a higher power can deal to you ? Especially if they have a very stacked Position 1 ninja means they have very high Injury stats.

Injury helps with damage a lot, especially considering that enemy back row ninjas mostly have low injuries therefore you can do massive critical damage to them.

Some testing with Injury by people turns out that "Every 100 injury difference vs your enemy is 1% more critical damage" (Not official info)

However based on this info we can say that "If you have 10000 injury on a ninja vs 5000 enemy injury you will do 50% more critical damage than you're supposed to" (which are quite high numbers actually taking into account that the 50% is calculated at the end of damage formula making it a big difference)

Combo = Increases chances of combo, decreases chances of receiving a combo (This refers mostly to standard attacks, sadly this stats is useless when it comes to mysteries and the "must combo" standard attack)

This stats personally I find the one that you can neglect the most except in some cases (for example: Jonin Minato, Kurama Naruto = ninjas who depend a lot on their standard attack causing a combo due to cooldown reduction so it can be very useful for them)

Overall it doesn't have many uses as Critical/Injury do which is why the stats doesn't have as much significance.

Control = Increases %chance of Controlling, decreases %chance of getting controlled (Refers to debuffs such as Immobile, Chaos, Sleep, Acupuncture)

This stats can be extremely useful if you don't have a healer/debuff remover in a team and you are not immune (Example: Classic Lightning Main blitz team)

Also can be extremely useful for helping you control (Example: using Masked Man / Susano Itachi this stat is a must)

Negative side: useless on some ninjas (Example: Roshi, Utakata, 6 Tails Naruto) (There is new Kushina now to immobile them but they regain immunity in round 2 anyway so control can only reduce small chance of them being immobile if versus Kushina)

By player info the rule for this stat is "Every 1000 control stat difference = 10%"

Which means if your ninja has 15000 and your enemy 4999 it will be practically impossible for him to control you.

Damage Types: You asked about skills that do Taijutsu and Ninjutsu, so in short if the skill has TAI tag it will scale off of the taijutsu stat, same for NIN, and skills that have both I think it will take into the factor of the highest one of the two, or grabs scaling from both at a lesser rate, essentially doing mixed damage.
Defense = Tai resistance
Resistance = Nin Resistance

How to Increase the stats:

-Refines (All stat - only 1 ninja)

-Purify (All stat - only 1 ninja)

-8 Gates (All stat - only 1 ninja)

-Ninja Tools (All except Initiative - all ninjas)

-Mount Myoboku Cultivation (All stats - all ninjas)

-Summon Cultivation (All stats - all ninjas)

-Battle Armor Rank (All stats - all ninjas)

-Clothings (All ninjas)

-Treasured Tools (only 3 Secondary Stats - 1 ninja)

-Charms (Depends on Cave Runes, All stat - 1 ninja)

-Cave Runes (All stat - 1 ninja)

-Bond Home system (All stats - all ninja)

Side Note: So as you can see these stats working together basically formulate together to create your own teams base damages depending on the stats. In short I do not think that skills really have base line stats they will always scale and create their damage based on these stats. I'm not 100% sure on this, but the skills that say they do damage, or cause heavy damage. Those skills definitely hit harder. As well as skills that say they ignore defense/resistance.

Regardless I hope this information has answered your questions and has helped you better understand the combat mechanics of the game.
Good luck! :)

** Information quoted from ICE* **