I took these:
4th lvl m/p crit rate (+40p/m crit rate)
4th lvl p/m def (+4% p/m def)
4th lvl p/m atk (+4% p atk and +6% m atk)
My dual class is still 85lvl so i took only 1st lvl p/m def (+3% p/m def)
And i think i will keep it till lvl 4 (+12% p m def) or will change to chance ud (+23% p/m def triger, cost 3 certificates) and for last 1 will take 1lvl p/m def)
In my own opinios the only thing u need for end game is p/m def as summoner to take less damage.You can get all in all +16% def pasive or 7% pasive +23% triger. And ofc +40 base m crit rate helps to crit more. w/o valakas and auguments i reach 250+ m crit rate - that means that every fourth my heal crits and from 4 dots + retriver I will get at least 2 m crtis :)
Hope this will be helpfull and see you in oly ;)
Ps those defences won't be bad for your yull either.