For Your stat abilites the tool tips are shockingly accurate so 10% reduction is infact 10% total of effected attribute according to testing from players across different servers. Weapon damage, Strength, Determination all contribute to both Damage for Auto - Attack and Weaponskills. The Auto-Attack total gains greater impact from a higher determination then Weapon skills but Str effects both similarly. For the actual equations check here.

http://valk.dancing-mad.com/?page_id=179