I haven't done thorough testing, but I remember precisely my Ghost Slash and Snipe/Multi Shot damage.

As far as I can tell :

• Raid : Jucy/Saran - only increases normal/spd/counter attack. No, my damage isn't capped, it's at 20%(mastery) 50%(Lina/Dellons)
• Gold Chamber : Yuu - matk is at 50%(Karma buff). I don't see dmg increase on both normal/spd attack and skill.

EDIT : OK, I did a re-check again, Jucy indeed boost both normal/spd/counter and skill dmg, but Saran still gives a boost only on spd/normal/counter, but not skill.

EDIT 2 : The only possible explanation is that level 40 mastery (10% dmg increase during skill) considered as the damage term along with jewels/lina/karon/dellons/v Lv75 mastery buff. Therefore, Shane dmg is already capped with just Lina's Warm Echo buff.