[atul]

The way I see it the point of using mages is to ensure you inflict more damage to your opponent than you receive. With SCs it's a bit of a win/lose situation, with mages and troops there's more shades of gray.

As to using mages in battles, I'd think you should never put mages in the field unless you have a specific purpose - especially in the early game they're more valuable researching or sitesearching.

What uses mages have, then? The way I see it, several depending on who they are. Also, nearly all the mages are going to need a screen of troops who protect them and do the fighting.

Boosting your troops: This helps your troops to overtake an enemy force with less casualities than without boosts - always good on a long run. Spells like Body Ethereal, Regeneration, Protection, Flaming Arrows and so on help either to minimize the beating they take or maximize the beating they give.

Supplementing your troops with summons: Raise Skeletons, Phantasmal Warriors/Wolves, Summon Imps and so on. Have battle summons do most of the work wearing enemy down (and taking most of the beating from their mages) so that your troops can mop up later on.

Cracking the toughies: In case there are some tough units in the enemy's army, try to find out the weakness they have (low MR, missing elemental immunity) and exploit it. Spells depend on the weakness.

General fire support: Ease the work of your troops. The spells can range from direct damage (Fireball, Lightning Bolt, Soul Slay) to scary stuff (Terror, Agony, Panic) to debuffs (Paralyze, Rust Mist, Entangle).

And of course there's the role of lone mage casting battlefield-wide destruction spells, not to beat the enemy but to inflict maximum pain.

As a general rule of thumb I'd say forget about personal buffs other than Quickness and those that boost either Precision or magic levels. The point is your troops are supposed to protect your mages, and if they rout your mage is anyway either routing or unconscious - fire shield won't do any good then. The first few rounds are crucial: less friendly fire, more time for summons to reach the front. Of course this is conditional, use protection spells to counter your enemy's attacks and so on.

So I'd say the question to be asked shouldn't be "what do I do with mages?" but "what do I do with mages x,y,z put against situation n or m?" The big advantage mage/troop army has against SCs is that they're usually much more expendable.

But, this is just an opinion of one guy, so take it with a grain of salt. And all the other usual disclaimers.