Do Dia and Bio Stack?

Introduction

A few days before, after I got scolded for casting dia after bio (I hit the wrong macro actually), the party disbanded soon. So I really wonder if what that guy said is true. "I've tested that. Trust me." He said. Bio, Dia and Poison all don't stack, according to that guy.

But I still don't really believe that they don't stack. He said "XX effect wears off" shows when the magic is cancelled out. I'd casted the 3 magic togehter numerous times before, still I never saw such messages! I checked the chat log, there was a message "The XXX is no longer poisoned" afte I casted dia. Thus I stop casting dia and poison altogether.

Another day in another party, the red mage casted bio and poison in one macro. And he put "/p Casting Bio. Don't cast Dia " in the macro. So I asked the party: Do they really cancel out each other? Everyone says he's tested it and "Trust me". If so, why my test results are different?


Discussion

We were at Whitehouse Sands, Valkum Dunes. I was blm/whm. So I started testing, but in my test on 10 tough crabs, there's NO such message. So???

A party member told me light and dark magic don't stack. Another said there's no need to carry out such a test when many people tested that and posted the result on forums. So I stopped that little test. That was an excellent exp party, and I didn't wanna break it.

Then, I really wanna say: When the 1st person says A is B without concrete proof, you wont trust him. When the 2nd, 3rd,...5th say so, you start to belive A is B. And when the 10th says A is A, you'll laugh at him!

Still, from what I learnt in Maths, a theory does not stand once there exists a counter example, even if you've got 1,000,000 supporting examples. And now I've got 10 counters!

Then how would I explain the supporting examples? I guess it was merely a coincidence. The mob is strong against that spell (say poison), so the effect wears off soon after it is received. And this is exactly the moment that the next spell (say dia) is casted.

Finally, have you ever tested it yourself? Don't blindly trust the posts on forums. You can see their words, but not the proof!

The next day, I've checked forums from the web. The information I can get is:

Bio II > Dia II > Bio > Dia
No info about Poison
Some say Light and dark magic are not compatible, and the elements next to each other in the element wheel would lowers the damages. This sounds logical.

For reference, the element wheel is :
Fire > Ice > Wind > Earth > Lightning > Water > Fire
and Light > Darkness > Light

And pls note that as far as I read, nobody stated they experimented that, or got the info from official sources.

IMOO, they do not cancel out each other, but weakens each other, so that the following decrease:
Damagae over time (DoT)
Length of duration
Damage
Enfeebling effect

NB: I havent tested that though (too lazy)


Conclusion

1. To be mp-efficient, don't cast magic next to each other in element wheel during chain nuking.
2. Cast the magic that can weakens the strongest aspect of the mobs, eg. dia for high defence mob (if most of you are meleeing), bio for high strengh mobs. If it's both strong in defence and strengh, well as you like, cast both or either, or cast dia if you like to finish it quickly, bio if you don't like to heal so much.