Board Thread:Questions and Answers/@comment-47.91.20.245-20180822055025/@comment-26447088-20180823200553

Yep, CTA Skill Boosts work on defense as well.

On defense, increase team skill chance passives only increases the chance of units activating their Rush, Multi, or Multi/Rush skills when they attack the enemy. I don't believe it increases the chance of other Passives or Uniques activating.