Let's just say....the people who have to cheat or use scapex to complete single-player are all noobs that need to practice against AI's on local game LMAO XD

I'd agree with most of the comments posted here. Yes, the game starts off easy and ramps up the difficulty quickly. Yes, there is a steep learning curve. Yes, it's more about learning what you have to do, and when, than it is about clicking buttons fast enough or trying to zerging-rush your opponent. Those who try to play this game as an FPS or an RTS will be frustrated. However, once you learn how to snatch up your own souls, redirect your troops to their next target, summon replacements, and throw offensive spells around, all at a dead run, then you'll find the AI a pushover.
Sacrifice is about thinking on your feet and changing your tactics to suit the situation. There's some strategic planning involved, of course, but the game is won or lost in the thick of the fight. Planning will only help you so far. I remember being stuck on Marduk for what seemed to be forever, the first time I played. It wasn't until I figured out what my wizard should really be doing that I was able to make progress against him. I needed to take out the enemy wizard while keeping mine alive so that I could start harvesting souls.
I think that people who get "stumped" by this game are simply locked into a particular approach (one that doesn't work) and don't realize they need to try a new angle.
-Khalaq

Can anyone give me any advice for beating that mission? I just can't figure it out, although admittedly, I haven't tried too hard. I think I lost it four times in a row, then quit the game. I'm thinking of taking a mission from another god besides Stratos instead.

First, save at the beginning of the level. Next, run around exploring the map until you've found the enemy altar closest to you. Reload your save, and then rush all the forces you have straight towards that altar and desecrate it. You may or may not have time to put up manaliths on the way.
Once one wizard is down for the count, the other will be forced to stay and fight.
On topic, I found the difficulty variable. Stratos' missions tend to be tough because, if you're playing with Stratos and only Stratos, your units tend to die a lot. James' tend to be easier because, though your units are slow, they're so tough that it doesn't really matter. Persephone's might seem hard until you get the hang of playing healer for your troops. Pyro's tasks can get difficult in the later levels, but once you catch on to the fact that the best Pyro army consists almost entirely of artillery, it gets easier.(Warmonger+Guardian=Death To All). Charnel's missions vary a bit, but can generally be made easier with liberal use of the Animate Dead spell.
Overall, I find that the game usually isn't that difficult. What makes it difficult is generally a lack of patience on the part of the player. For instance, say you're presented with a wizard attacking your altar. If you kill the wizard first, you can collect all the souls of his troops and cripple his army for the rest of the game. However, since the wizard has protective spells and tends to run around a lot, this can be difficult to do, and while your troops are chasing him, the enemy is shredding your troops. Alternately, you could kill some or all of the enemy troops, and try to kill the wizard before he snaps all their souls back up. This route is safer, but it means more work later when the wizard comes back.
The "Perfect" sacrifice player would probably be the kind of person who could do exactly what the posters above me describe: Just sit around by the altar, wait for the enemy to come, shred 'em, gather up the souls, summon more troops, and repeat until they stop coming. Personally, I find that boring, so maybe my playstyle of "hunt down the wizards and beat them up for lunchmoney-souls and then assemble a massive horde to overwhelm everything" makes life harder for me. But I don't care, because I have more fun playing that way ;).

This game isn't so difficult. I've tended to think that the game is extremely hard to finish, but later i realised that the key to this game is being defensive and use the guardian spell effectively in the later period.
You may make all of your creatures guardians (in the last levels), if you want to advance later you simply have to kill your own creatures (hold right click then find the "fist" icon). Don't forget to heal the guardians (get Persephone's scarab for that!)
Always pick the enemy wizard with artillery, get the spell animate dead (Charnel level 5) and you can't loose the game.
If you suck up with the enemy's dead spell or volcano just try get near to the enemy spellcaster ONLY with your wiz and leave the army behind. This is very good against Marduk, who really likes to cast the reaper upon you, but he is enough stupid to cast it on your lonely wiz lack of the army as well, so death will cach his own army instead of yours.
Briefly i think the defensive bunkering is the best tactic for most of the missions (with few expections).

Sorry, didn't see your question for over a year:) In case you or anyone else still needs it:
Here's my Blitzkreig strat:
Open options and set a hot key for 'Go To'. Summon Seraphs and hotkey them. Use the Go To hotkey and right-click on the map to make them explore the map at lightning speed. You will be able to see the manaliths on the map. Use the Go To hotkey and right-click on the manaliths. Guardians or not, the manalith will be dead.
Simulaneously haste yourself and run in the opposite direction (if you sent the Seraphs clock-wise, go anti-clockwise) solo and attack another manalith simultaneously with your spells.
Once you have gotten a safe lead (Neither of them has more than 2 manaliths, run to an enemy altar and call your Seraphs to you. Sacrifice one. When the ritual starts, he will run to fight you to save his altar. Command your troops to attack him from long distance my attacking with Go To. Also haste yourself and rush to him and attack him with spells.
If I remember correctly you get a boon for killing one of the two quickly before reinforcements arrive to help you. The other guy will fall easily once alone.

What can I say? I'm a powerful necromancer:)

Those cheats dont come up. And this game has got ridiculously hard :(