[BB Shockwave]

Not sure you are doing this right, using Catapults - a unit noteable for its fire weakness - with units that excel in area effect fire damage like the Archdemon (now in DS). Btw, that game sure munchkinned the Archdemons, giving a Level 5 unit that can teleport anywhere the ability to use strike-and-return without retaliation is not even funny. That game is unabalanced as hell.

I only have tips for Crossworlds, I am playing No-Loss there and have gone through multiple times with different army setups. My first was Warrior on Normal, No-Loss, all-LIzardman army. I skipped using Gobots and Chosa because they die easily, and the Chosa is useless for anything else but summoning.
My second was Paladin with Human army on Hard - I used Rune Mages, Archmages, Horsemen, Paladins and Royal Griffins. The latter are a great synergy for humans. I sometimes swapped Paladins with Knights, against Dragons.
Now I am going with a Mage and Demons, on Hard. I use all demon units, plus Demonologists, got to level 38 already, no-loss. The key is getting Order Magic+resurrection first, and getting the necessary demon-army-booster items like demetrius or the Bow of Thousand Souls. My main line-up is usually Executioners, Demonologists, Demonesses, Archdemons and Cerberi. For tough battles with fast enemies I replace Cerberi with Demons, and for enemies I cannot charm I replace Demonesses with Scoffer imps (since Taunt works with the undead, too). Archdemons are there to halve enemy troops and soak up damage from weaker troops, I usually weaken one enemy with death Star/Fireballs and then use my Demoness to swap that with my Executioners and use my Cerberi to kill the teleported unit. Demonologists are good for summoning and healing, but they otherwise suck as ranged units. Demonesses help a lot by charming enemies whom you can sacrifice. They are also quite powerful if you use the whip (I don't, since the bow is better) and have Agvares as a follower.