Focus bow,and not sure about acumen on weapon but unless you reach cap without it acumen it is.Attribute doesnt really change much,all your nukes are unelemented until you can enchant mark retriever/Invoke(wich is at 98 and 99) so Fire/Holy/Wind/Water are all good,dont get earth or dark cuz lots of mobs are resistant to them.
Most of the good summoners for XP are using Damage Up on there bow and empower on there retributer. The best PVE tat setup is +15 str.
Summoners dont really need casting speed in my experience.
Summoners do not need critrate in my experience either, the difference between focus and non focus is not that significant, 370 critrate on the cats and 400 critrate is almost non existant, so might as well go for the 300 extra critrate which gives the pets far more patk fully buffed then the focus methodology. IF double SA then focus is clearly the best choice after Damage up.