Regarding Machaka: Slow the spiders down. Especially Prison of Fire and Quagmire, but also False Fetters, Encase in Ice, Earth Meld and Storm of Thorns (if you've made it that high in Evo) are the things to stop the spiders. Your missile troops and evocations will make short work of spiders as long as they do not get into contact with you.
MA TC has *beautiful* paths for some amazing combat magic. The Acid thingies, Magma thingies and Gifts from Heaven, you have all those at use.
As an example, lets take a situation where you have no items and very limited gold at use. Recruit five Imperial Geomancers. Script the four Geomancers highest on the list with Communion Slave, Hold, Body Ethereal, Gifts from Heaven x 2, Spells. The geomancer lowest on the list is scripted, Communion Master, Power of the Spheres, Summon Earth Power, Body Ethereal, Personal Luck, Spells. Each of the slave geomancers are thus boosted to E3S2, while the master is E5S4. Each Geomancer will get off about two GfH before they pass out, and that should be enough unless you are facing a massive enemy army (and then you wouldn't just field five Geomancers, would you
).
Another example. You mentioned you have lots of Imperial Alchemists and lots of hammers at use. You can craft a bunch of Slave Matrixes and a Crystal Matrixes, as well as a Crystal Shield. Give any mages high on the commander list Slave Matrixes and an Imperial Alchemist low on the list the Crystal Matrix and Crystal Shield. When this bunch enters combat, they all are in an instant communion with Power of the Spheres in effect; that is to say all of the mages with a Slave Matrix start with +1 to the magic paths without any fatigue. Now the communion slaves are scripted with whatever you want them to do, while the Communion master does the buffing (Summon Earth Power, Summon Phoenix Power, Mistform, Eagle Eyes or Wind Guide (if you have large enough communion so that the communion slaves do not pass out by the fatigue caused by the Wind Guide), Strength of Gaia etc. Notice that you can add in more slaves (Geomancers) who are scripted with Communion Slave, Holdx4, Stay behind troops, they will help to spread out the fatigue from the Communion masters spells so that the Imperial Alchemists won't get too much fatigue from the buffs. If you add in more communion slaves this way, you should consider handing out more Crystal Matrixes to get more Communion masters, to speed up the buffing. Anyway, you should end up with Imperial Alchemists with effective spells elemental levels at four (and more if you handed out to them items to buff their spells levels; water bracelets, earth boots etc). Nothing in the world the AI will be able to throw against you will be able to handle the storm of Flaming Arrows, varios Acid and Magma spells, Falling Fire and Frost, while your effectively Nature 5 mages take care of the army wide buffs (Relief, Mass Protection, Mass Regeneration, etc).