Yes. I usually go for Commanders when I get champions without decent mage spellbooks (or without any spellbooks), and also when I'm playing a more army-focused game rather than a magic-focused game.

I also on rare occasions choose to specialize for some type of melee combat on my sovereign and take Defender, Warrior, or Assassin, but that's pretty rare, and I wouldn't do it on most champions.

the role I pick the least is warrior. Assassins are way more efficient. However, as for the rest, they all have their place. Defenders for when you don't have a solid fortress up and running for meatsacks. Commanders for ...unique...abilities... and then a couple of mages to obtain the spectrum of magic.

I tend to play the game by casting no magic throughout. Especially if I'm playing a faction where I feel should be non-magical in nature.

I play single hero army with assasine. It feels good to play a character who rules the map like a demigod and kills armies of dragon as single unit .

And he got mostly all spellschools by killing the other heroes you get over fame.

Assassins can do more spell damage than mages. Assassin is secretly a spellcasting class, especially with equipment/abilities that gets crit chance above 50% and increases crit damage. They lack the consistency of mages, but with AoE spells they are almost guaranteed 1 critical hit.

Not saying assassins are BETTER than mages - I am saying that they have the potential to be better.

Give a sovereign the warlock and brilliant traits, level him/her up as an assassin. You'll see what I mean.

Yes. Getting a critical on flame dart is basically an instakill. When your fireball hits 3 targets but 2 are crits...you get the idea!

My sovereign is always a mage, but my heros are usually defender or assassin.

My sovereign is almost always a mage and my first hero is almost always a commander. I always choose the research and gildar skills--although I'm not sure if the +1 research/gildar traits stack. For example, if I have the +1 and +2 gildar per turn traits, do I get a total of +3 gildar from the hero every turn? Same with research.

It depends somewhat on his spellbooks, but I have experimented with making my sov a commander. It works quite well given the fact that he has -10% unrest modifier compared to normal champions' -5%. This allows me to run my capital with max efficiency earlier, giving me a push on that exponential development scale.

In my last game I tried this with Relias despite his fire/air combo and even that worked out fine.

PS. The commander tracks do in fact stack. Merchant IV gives you +14 gildar/season. Tax free.

1. Civilization

I picked Altarian Blood (10% exp, Rush) I chose Warrior Caste (+1 level for trained units), Tough (10% HP), Quick (10% initiative).  I also picked Enchanters (build scrying pool for 1 essence) for the sole purpose of army enchantments. Then picked rebels for weakness (10% unrest) which actually feels like a poor choice but works well with the story for my civilization.

2. Sovereign

I chose Altarian.  General (25% army exp) for profession. Tactician (+1 army initiative), Hardy (+1 hp per level and poison resist), Life Magic (for healing and preserving troops), Earth Magic (Preserving troops as well as Production enchantment for war machine.) Air magic could probably have worked well here instead of Earth, but either seems fitting.

3. The Commander

I've decided this class fit the role I wanted to play very well. I immediately took Potential (+15% exp hero only) , then leveled up Tactician (1 army initiative) until I got Battle Cry (ability that allows all army units to act immediately), Enhanced some life magic for healing and Shrink, Growth. and am currently enhancing Leadership (+10 accuracy) to work on Trainer (+10% exp)

Now, as you can see, I've created an entire civilization and hero class with various possibilities for synergy.  Creating synergy is when you combine elements of a whole (such as skills, abilities, etc.) in order to create something greater than the sum of its parts. 

With a sovereign such as a Commander (whom many people are often quick to dismiss as a viable choice) he receives

1. Potential of up to 100% bonus experience progression for all troops under his command (Trainer IV, Altarian Blood, General, and Potential trait for individual army creation).

2. Potential for high Initiative for entire army, with or without Haste Spell, which consumes mana (Tactician 3, Quick). Individual Troops can also benefit from +Initiative gear, the Fast trait, or Aura of Grace.

3. Potential for High Hit Points. Since armies will rapidly gain levels, abilities such as Tough, Endurance, Constitution, or Aura of Vitality work well.

4. Abilities such as Battlecry and Rush work very well together, and can ensure closing in on your enemies quickly. I haven't tried Command, which looks useful as well.

And that's it! With a little bit of improvisation, you can tailor any hero or civ to specifically fit your needs.  I hope this post answers some, if any of your doubts about choosing something other than a mage. Thanks for your time.

Like most of the people here, I have a Mage Sovereign and my first champion is a Commander.  I like the summon spells for the Mages to help in combat, and I like the ability Commanders have (I think it's called Rally) that gives all my units an extra turn (it's an end-tree ability, but it's really good).  I also like having the Commander for road-building when I'm not playing Mancers (which is rare).  Sometimes I'll make another Commander and level him just enough to get Administrator III if I have a lot of cities.

Other champions I get generally already have their class, so I don't get to pick there.  I'll put my Warriors on a horse and given them any berserking weapons I have, because with the +damage bonuses they get, they can really tear it up.  I haven't found much use for Defenders, but I like to play on Huge maps, so by mid-game I should have 7 or 8 armies walking around the map (if not, I'm probably about to lose).

Mage is the obvious choice for Beastmasters, both because of the mana cost reduction and because of the bonus to Spell Mastery (it really sucks when a Hoarder Spider resists your Tame).

My favorite is Assassin ... using bow or high crit multi dagger. Weak but immens damage and high initative with somtimes 90 dodge.