Okay another try…
Using the same teams and different items (10xheal - 5xAxes - 5xTimeStop - 5xBomb), let see the result,… drumb bell please… 
I already use 80% (8x of 10 heal) and 1 axes in start of boss stage!
but nevermind, I want to know what the rest items can do, and specially TimeStop.
Well, I after using the right time, so before boss mana full I use TimeStop,… and the result is comfortable, they drop mana to zero, and delay the slash attacks… wow…
So, use 3x ManaStop and 3 bombs, all gone… puff! Victory!
Well now, all 10 trials is finished stage 3! Achivement done, next achievement is use without too many expensive items.
Emblems Monk for Wilbur, Cleric keep for Rigard (later after I can get from TC20 or summon).
Trainer for Poseidon.
Thank you @Scarecrow for the suggestion! 