I would assume it is the same as with any other skill.

25% to trigger 'roll acc against res to see if it will stick'.

that means skill use initiates one roll, then only on success - roll again for effects.

i have too few tries to conclude anything, but I was expecting more buff strips on my shaman against magic keep - that would mean acc takes part in here as well (unless as stated - rng bias due to small number of tries)

Yes, you need Accuracy.

Debuff’s can be broken down in 3 phases:

PHASE 1: CHANCE %

25% chance to attempt to remove a buff.

• Your attempt should fail 3/4th the time.

You shouldn’t see anything in the fight.

If the 3/4th attempt is a failure, you don’t move past phase 1.

• Your attempt should succeed 1/4th the time.

You should see something in the fight.

If the 1/4th attempt is successful, you move to phase 2.

PHASE 2: ACCURACY VS. RESISTANCES

Shaman Accuracy will activate to target the skill on enemy.

• If Shaman Accuracy is higher, You should see the buff removed from enemy in the fight.

Enemy Resistance will activate to resist the skill. 

• If Enemy Resistance is higher, You should see a green text message pop up on enemy hero in the fighting with word “Resisted”.

Lastly, The game has another aspect associated with Affinity match ups which effect Debuffs.

PHASE 3: AFFINITY MATCH UP’S AFFECTING CHAMPION HITS

You need to remember Shaman is Force Type (Red).

Shaman’s Weakness is Spirit Type (Green).

Debuffs can only land if the Hit you are doing is:

• Crit Hit
  
• Strong Hit
  
• Normal Hit
  

Shaman can’t land any Debuffs if the Hit is a Weak Hit.

A Weak Hit is only possible vs. a Weakness Affinity. (Spirit Affinity in Shaman case).

You should try to avoid using Shaman Skill vs. Spirit Heroes.

You run the extra risk of skill not succeeding.

IN SUMMARY: 

• You should always look for heroes with 100% chance
  

This removes Phase 1 from the Debuff process.

It makes applying Debuff’s a lot more manageable.

• You should add a high amount of accuracy to ensure your skill isn’t resisted.
  

Enemies Resisting your skills can cause you to lose a fight in a critical battle.

• You should avoid Weak Affinity heroes.
  

A Weak Hit doesn’t do a lot of damage to target hero.

A Weak Hit is doom for your Debuffs.

That's all well and good, however the Shaman's remove buff skill is not in itself a debuff - i.e. it does not place a red debuff icon. I too am confused about abilities such as these, as well as other abilities such as buff steal and turn meter reduction skills.

These skills are not debuffs, as they do not place red debuff icons, or linger for 1 turn or longer. It's unclear whether accuracy is important for these skills or not, so as the poster suggested, could someone in the know please respond?

Accuracy and resistance specifically state 'debuff' skills, however it's unclear whether this is poor wording. We need to know what the devs have done with their programming. Do skills that negatively impact characters, but without placing a debuff icon, count, or not?

Buff steal.

Buff neutralize.

Turn meter reduction.

There could be others, but I can't think of any.

I don't know whether placing accuracy gear on these kinds of heroes is a waste, or not.

@Isawa, any skill that does something against your opponent hero is a Debuff.

If you decrease enemy defense, you are doing something vs. opponent hero.

If you remove a buff, you are doing something vs. opponent hero.

If you have any doubts, you can look at Shaman A1 more closely!

Shaman A1 removes random buff with 25% chance.

BUT NOTICE WHAT HAPPENS IF WE WAS TO USE TOMES ON SHAMAN!

The skill upgrade Lvl. 4 Buff/Debuff Chance +5%

The game is considering the remove random buff as a Buff or Debuff.

We can rule out Buff because it is happening to the enemy.

So the skill can only be a Debuff which means you need Accuracy for it to work.

Player J said:

@Isawa, any skill that does something against your opponent hero is a Debuff.

If you decrease enemy defense, you are doing something vs. opponent hero.

If you remove a buff, you are doing something vs. opponent hero.

If you have any doubts, you can look at Shaman A1 more closely!

Shaman A1 removes random buff with 25% chance.

BUT NOTICE WHAT HAPPENS IF WE WAS TO USE TOMES ON SHAMAN!

The skill upgrade Lvl. 4 Buff/Debuff Chance +5%

The game is considering the remove random buff as a Buff or Debuff.

We can rule out Buff because it is happening to the enemy.

So the skill can only be a Debuff which means you need Accuracy for it to work.

One thing you need to consider is that this is just a generic description. Note that it says 'buff/debuff', but clearly this is not a buff. If the developers were being careful with their wording, it would only say 'debuff'. Why would they leave the word buff in there?

I think a much better approach would have been to say 'ability'.

The wording is not a certain argument. To make my point, I'll post their definition of debuffs from this website, which provides the opposite argument.

Buffs & Debuffs

One of the most principles in RAID: Shadow Legends is the use of buffs and debuffs. These are effects that alter the performance of a Champion. Beneficial buffs can briefly improve a target’s stats or abilities.

Debilitating debuffs add a degenerative or damaging effect that reduces the target’s abilities in combat. Unlike buffs, a debuff will only stick if the target does not have the power to resist it—something determined by Champion’s Accuracy and Resistance stats.

Buffs and Debuffs are displayed near a Champion’s HP bar and are displayed in blue (for buffs) and red (for debuffs). At any point during a battle, you can tap on the INFO button at the bottom left and see all buffs and debuffs currently in effect on your squad.

This is quoted directly from this website. Note the final paragraph, which implies that debuffs are only abilities displayed as red icons. Abilities such as the Shaman buff dispel, turn meter reduction etc., do not place red icons. The true question is whether this is poor wording, and these abilities are actually debuffs, or whether debuffs, (and accuracy/resistance), only apply for abilities that place the red debuff icons.

Can someone from Plarium please clarify, as this is important to know, and the current literature is unclear.

Thank you!

Isawa, you can ask Plarium anything you want.

I’m just telling you this is how Shaman has been since the beginning.

A lot of Debuff do show a red icon, but not all of them.

I think the final paragraph could have been worded differently, but it is partially right.

I don’t think the game will change anything to be honest.

It seems like such minor wording issue that they probably will not bother.

Thanks for the input, but I'm not asking for anything to change. I just want clarification on whether accuracy affects skills that remove and steal buffs, or reduce the turn meter.

Due to the ambiguity of everything ranging from skill descriptions, to the game website, it's a murky area. Only the people who code the game can tell us whether it applies, or not.

Isawa Hochiu said:

Thanks for the input, but I'm not asking for anything to change. I just want clarification on whether accuracy affects skills that remove and steal buffs, or reduce the turn meter.

Due to the ambiguity of everything ranging from skill descriptions, to the game website, it's a murky area. Only the people who code the game can tell us whether it applies, or not.

Bumping this for specific clarification on Turn Meter Reduction. In arena I regularly observe her not successfully popping her 3's turn Meter Reduction, though there's no observable "Resist" occuring.

Rughes said:

So according to that, it makes my Septimus worthless without maximum accuracy? Becouse he is not able to increase debuf duration on enemies without that?

I am not entirely sure about that but like 90% - you need ACC to extend debuffs (Vizier or whoever).

I do not know about TM reduction or any other 'not strict debuff' but I would say the same - if it affects target negatively - there is ACC against RES roll while trying to apply.

% chances in skill description mean 'chance that roll ACC against RES actually takes place'

+x% in skill description after booking it means better chances to roll for success (against not even rolling at all - same result as failing roll)

25% base chance to do this or that debuff on unbooked skill means on average 1 in 4 hits will roll acc / res part, 3 out of 4 wont even roll that and do nothing extra

+10% on lv3

+5% on lv4