Resto Sham -Tidal Waves/Tidal Chains Bug

[Healmasta69]

Resto Shaman Weapon Sharas'dal, Scepter of Tides Bug:
Tidal Waves tooltip without artifact weapon says 30% reduced time for healing wave and crit chance of healing surge by 40%. But with the artifact weapon equipped a certain talent tree in the artifact(Tidal Chains) allows the tidal waves to increase further or so i thought. With the artifact weapon on and casting riptide to show the Tidal Waves, the tooltip only shows a small increase(15% with 5 points in Tidal Chains). Tidal Waves with the artifact weapon shows 45% healing wave reduced time, and healing surge crit by 60%. I currently have 5 points in the Artifact Talent - Tidal Chains. Tidal Chains says it reduces cast time and increases critical effect chance by an additional 50%. But when you cast there isn't a 50% increase at all. Considering that the tooltip of Tidal Waves only increases by 15%. We are currently missing 35% additional bonus to the Tidal Waves.

Update:
Without Artifact Weapon Sharas'dal, Scepter of Tides, Tidal Waves - 30% reduced cast time of Healing Wave/Healing Surge critical by 40%.
With Artifact Weapon Sharas'dal, Scepter of Tides, Tidal Waves - 48% reduced cast time of Healing Wave/Healing Surge critical by 64%.
6 Points in Tidal Chains(Passive:Tidal Waves reduces cast time and increases critical effect chance by an additional 60%.)
I'm pretty sure something is messed up with one of the 2 spells/abilities or both who knows. But the math doesn't add up. With 6 points in Tidal Chains, it only shows an 18% increase in reduced cast time of Healing Wave and only a 24% increased critical chance of Healing Surge with Tidal Waves active.
Multiple tests within dungeons and outside has shown this.

Can anyone confirm this?

[Ahovv]

The bonus seems to be multiplicative to your existing one. For example, a multiplicative 10% reduced cast time to an existing 30% reduction will result in a 33% cast time reduction. Since this bonus seems to be applied to the base 30% talent, each incremental trait point adds 3%, which is why you are seeing +18% with 6 points.

Whether or not it is a bug is unknown.

[coprax]

There is a difference between percentage and percantage points, 40% healing surge becomes 44% with 10% increased chance.

[Healmasta69]

So do you think that the tooltips are being displayed wrong? As in to say an additional 60% wouldn't really be 60%? It kinda makes it very confusing to calculate for healing. I mean if it is just increasing by 18% then why wouldn't it say that instead of saying "an additional 60%". Usually when you say additional it means you are adding it to the original.

[Deleted]

The percentages on Tidal chains are multiplicative not additive so that means 5 points (50%) is a 50% increase to what you already get. So 30% shorter cast is 45% shorter cast and 40% increased crit is 60% increased crit.