Proper tactics are especially important in the early game, when the enemy great mages (and neutrals) remain a great threat before you load up on advanced units, perks, and upgrades. Setting up your assault or defense is about more than merely supporting your ground forces with ranged units--you must take into account the enemy units strengths and weaknesses, the terrain, and how a properly used spell could affect the battle. Great mages are fond of summoning monsters, so a thin defensive line could be easily bolstered by elementals with a flash of magic. Like in Civilization V, cities can defend themselves; this is especially troublesome (or helpful, if you're on defense) when a ranged unit is in the city hex. You also need to watch out for wandering monsters; when one appears, you're never sure if it'll attack you or the enemy.
You can skip Warlock's combat and movement animations. But consider watching them, because it's fun to view your units in battle.
Warlock's diplomacy doesn't allow for anything more sophisticated than a peace treaty or demands for gold or mana. You might also take issue with the lack of research or victory options; you can win the game only by defeating your foes, casting the unity spell (which grants you an automatic victory), defeating a god's avatar, or claiming all of the holy grounds on a map. But Warlock wasn't designed with diplomacy or research in mind. Constructing buildings has but two goals: to sustain and to upgrade your war machine. The same goes for exploration--your recon forces fan out not to find wonders but to locate suitable resources for new cities or to look for enemies, monsters, and other neutrals to pound. Diplomacy is useful only for bullying your enemy into giving you gold or mana instead of issuing an outright declaration of war. You won't find alliances or research agreements in Warlock.
How are Warlock's great mages at warfare? They fare better on defense than offense. The enemy great mages (sadly, these aren't hero units, as in Master of Magic) that lead the opposing forces understand how to flank, and they even get some of the more advanced concepts. Playing on challenging difficulty, an enemy mage will place a unit of donkey knights among a group of resting warriors, preventing the forces from regaining health. It constructs defensive fortifications that lay down overlapping fields of fire, or it snipes at you from its borders thanks to the extended reach of the magic tower's mystic cannons.
The enemy great mages are capable of making some boneheaded decisions as well. Undead units are immune to death magic, but the AI may use an advanced unit, such as noble vampires, to blast away at lowly skeletons, who are immune to their magic-driven attacks. Or it will attack ghosts, who are immune to physical damage, with melee units. Enemy great mages tend to neglect using middle-tier and higher-tier units, favoring conjured beasts and hordes of starter units. Waves of skeletons, bats, and conjured wolves fall to a single, buffed unit. And the AI has problems discerning which of your units is the best to attack. The enemy mages don't always press their attacks, either not sending enough units or failing to isolate your forces.
Warlock doesn't make good use of water spaces; they're essentially highways for getting from one landmass to another. Sure, you may find some floating treasure or monster lairs (and monsters such as giant fish and krakens), but the only way to exploit these spaces is to build either a harbor or a fishing village. It would also be handy if the game communicated the benefits of certain spaces, such as how terrain affects combat and movement. But even the manual and beginner's guide lack this basic information.
You gain spells through research. The pentagram-like presentation looks nice, but it doesn't show how a given spell path increases in power.
In fact, the manner in which Warlock presents its information is its major flaw. The game and its manual lack information trees. You would think that the tax office, a building that boosts a city's gold output, would be something you would gain access to if you built other gold-producing structures. But to gain access to it, you need...a rogue's guild. The system for researching spells is even more confusing: you may select one of five options, but again, no trees exist inside the game. The logic in which the spells appear as research options is difficult to discern. You can find some of this information on Paradox Interactive's forums, but that's no substitute for proper in-game communication.
Warlock: Master of the Arcane is pretty good as it stands, though. It offers a reasonable challenge at its higher difficulties, presenting its best face--combat--almost immediately after you start the game. It's an incredible rush the first time you hold off an enemy great mage's swarm of units as it attacks one of your cities or you make your final push toward the foe's capital. There are some problems here, but Warlock feels fresh enough to keep you squashing the opposition until the wee hours of the morning.