It should read either with 1 pc equipped or with 5 pc equipped. If just one then yes, if 5 then no. Each armor tree has either one or 2 five set passives. I only know the ones for light and heavy off of the top of my head.

Also they should stack

Evasion grants Major Evasion and Hist Bark grants Major Evasion while blocking when wearing 5 or more pieces of the Hist Bark set.
Identical buffs do not stack.
If one were to grant Minor Evasion they would stack, but since both grant Major Evasion they overwrite each other.

Armor skills require proficiency in their respective trees to learn but do not require their armor types to be used. Light Armor mages use Immovable just as Heavy Armor knights use Evasion. The morphes of armor skills reward using the armor type they were meant for but never penalize using another armor type (i.e. Shuffle, a morph of Evasion, grants 0.5 seconds of snare/root immunity for each Medium Armor piece equipped).