Since I don’t use Arnold, I’m not sure if it supports Maya glow. The glow intensity slider should be there unless something changed in Maya 2016 EXT 2 (which would be an odd thing to remove). Can you provide screenshots?

Honestly though, I’d do the glow effect in post for a couple reasons:

-More versatile looks. Each Maya scene has one glow regardless of the different intensities per shader (the shader glow you see in Hypershade controls the look for all glows in a scene)

-If for some reason you have to adjust the glow, you don’t have to re-render the 3D scene