Even though it depends on the equipment one does found, I think a decent early game formation is

1
----5
2------8
----6-----10
3------9
----7
4


1: Detective Kaine
2. Princess
3: Khouri (Witch Doctor)
4: The Lion
5: Lumberjack
6: Merci (Mad WIzard)
7: Nate Dragon
8: Sasha
9: Natalie Dragon
10: Panda

This one totally focusses on Buffing Merci and Nate Dragon (both with highest DPS). As soon as the "Storm-Rider" Ability is ready, pull in Thalia to use it.
The point of using Kaine and Panda is to grind Gold (+1000%). As soon as you get to a boss level change :
Panda -> Phoenix (for 25% by death)
Kaine -> Bush Whacker and put Bush Wacker somewhere were he gets Bonus from Wizard and Nate Dragon and then go click like a beserk!

Just my 2 cents

my current formation is :
1
----5
2------8
----6-----10
3------9
----7
4

Levels are:
1. Artaxes: 200; 1% CC;
2. Nate: 163; 25% BD, 2% CD, 2 EP;
3. Panda: 80; 5% ACD; 50% GF; 2 EP;
4. Primcess: 130; 5% ACD, 1 EP;
5. Kaine: 600; 5% ACD;
6. Natalie: 550; 10% GF;
7. Jim: 701;
8. Sasha: 630; 5% ACD, 50% BD, 1 EP;
9. Khouri: 150; 5% ACD, 50% BD;
10. Merci: 200(no upgrade yet though); 25% BD, 5% CD;

Total dps: 233Q, every char is at 4-5 XP(although for some reason 5th xp point gives me no dmg boost :-?)

Note that I use this for Bosses, when just grinding I switch Nate with Kaine for more gold.

Index:
ACD = All Champion Damage;
BD: Base Damage;
EP: Enchantment Points;
GF: Gold Find;
CC: Crit Chance;
CD: Click Damage;

I have tried that strategy, unfortunately its not very practical. Almost always you want Sasha on 2nd row for the DPS increase.

Monsters will stack indefinitely if you don't have the DPS to kill them off. DPS > all in this game.

Theoretically it could be a good strategy to stall boss levels, however, almost always you can kill off the boss wave with all your dps skills + clicking.

The best defense is offense in this game. Kill them all before they reach you is definitely the way to go.

I shouldn't say the best actually, I mean a very effective method. Depending on gear and such perhaps a burst is better.

Never mind... I switched to Sils and got much improvement. Thanks!

I am stuck on level 89 what is the best crusader set up to beat this level?

So, what should the best formation be then??

The "best" formation is different depending on the items that you find. Here is mine so far in the new campaigns.

http://i1053.photobucket.com/albums/s468/metafalica/crusaders.png