Thinking about artifact combos and was wondering if shields stack. Example would be if someone on the team is wearing the 4-piece shield that gives a shield worth 30% of the wearer's max hp to each member and if another hero has a 2-piece divine attack set that gives a 15% shield. Would both shields from each set stack or would just the higher of the two be in effect? 

On a side note, does anyone know if the Rejuvenation mastery "heal" is also applied to lifesteal?