Does the phase acrobatics stack from perfect form stack with the one on the tree?

no

You get one total and its not worth wasting a chest peice over.

What else should I use on my ed contagion then?

if you want faster mapping, qotf

if you want balanced dmg/defenses use cherrubim's

some people do use perfect form too, its good for bossing and it'll save you passives in tree

Free artic is nice.

Yeah it seems to be pretty dank..