Hi Leonard,
1) With my drake as the DD i do around 200k per run (without proper units and training). My drake is a zeus faith and around 6.5k atk.
2) My kahuna faith is Athena but i suggest u focus on DEF because survival is the key to cosistent insane trigger. SW Kahuna only benefits from MAG when he is using his active skill (just to increase one healing tick to have more trigger chance and compensate Berserker Vincent debuff [poison] if you are using him)
3) i usually trigger around 4x~8x or the highest i have achived is 15x. Rarely fail to trigger at first atk. But keep in mind that i don have proper unit required (Example: Im using GS/GR Kane in my squad) so i guess u are just having a bad day.
4)Vampiric runes is better since kahuna trigger chance is 30%. Compared to Double Strike runes have a 20% chance at max lvl. Since RNG always dissapoint us i guess 30% Lifesteal is better compared to the extra IF i proc a double stirke then i get a new 30% chances agn. (Lazy to do the calculation, having maths exam tmr)
5) About the poisoned tile, I noticed the skill Acid Pool from the snake head is always aim at my backline. Example:
GR Kane - GS Kane
Dragoon Drake - SW Kahuna
Zealot Leon
Acid Pooil always aim here
Unit - Unit(HERE) - x
Unit - Unit - x
Unit - x - x
If you have a MB Miu u can keep silence the snake head with the insane trigger chance. What i do is i just run away if it aimed at my GS Kane or try to use potion(shield) on my kahuna
Would u mind posting a picture of ur squad so i could see what i can help you with?