The answer is: yes and no.
If you have windspeaker, mikael, runic armor and redemption, your heals on yourself (or shields) will be 38% more effective.
The increase of shield and healing power on item are UNIQUE passives, wich mean you cant stack them.
However, if lets just say you have redemption and then you buy mikael, the 10% increase healing/shielding power will become 20% because mikael has the highest number.
Windspeaker will alway stack with items and runic armor only increases the heals and shield on yourself.
Hope that helped! if you have any other questions, just leave a reply!