How to win in ambush? Of course you must smash all the enemy troops. this is quite hard for wizard, as mentioned above. the main damage output of wizard faction come from the hero's spell. So my strategy to win was below: 1. choose right mini art for your troops, especially your egg.
My choice was hp, def and luck. the reason was to let your troops stand as long as possible so your hero can deal more damage.
if you have got wizard level 8, I think you can use hp, def and speed. speed was better than luck. 
2. choose right talent for your hero in ambush.
for level 8 hero---> magic mirror, basic erudition, intellect
for level 9 hero---> basic erudition, mana recovery, basic sorcery
3. the most important thing to win ambush
put your egg to the cornor of the battle field at the right moment. 
:D
