I haven't player empyr yet.
I've played Esus a few times and here are my observations:
After I get the religion (and spreading it to all cities without building a temple is a big boost) and guilds (for shadows)...
1 note: Sometimes Esus will not spread to a particular city for awhile. I can go to another city and spread it there, then go back, and by then it will spread to the original one I tried. I have no idea why this is. Could someone explain? Of course, it is my state religion, but sometimes it just will not spread to a city (I do not have the option to do so with my Nightwatch).
Then...
Maybe research summoning just to get Gibbon, but he is just a summoner and 1 pit beast hardly has an impact on my army (or any single summon, for that matter). This makes me want to build adepts early and make conjurers to go with my shadows, which is nice for fodder but not really carrying any 'cool' factor, as stacks of Tier 2 units (conjs), spam summoning 4-6str units is just too stackerific for me. I'm more of an "A-team" kind of guy.
Well, maybe horses since the prereqs are done, it seems logical. That would give me 3 warhorses and some horse archers to bounce around...
Or Rage, to pick up berzerkers...
If you manged them all, you'd have a decent mixed stack of an army, but if you get only 1 or 2 (of the above) you woefully lack variety and strength.
As usual, the best option for bombarding is fire mages

sad

, because they can promote mobility and be hasted.
In quick speed, having a 1 move non-living unit (catapults) is silly. Taking spells (and assassins) each step, as you slowly approach an enemy city, means catapults rarely get to attack (or even bombard). This is because only movement is not scaled, and the production possible while a 1 move army approaches is sufficient to slaughter them in almost all cases. Note, this might not be true in SP - perhaps the AI will let you walk
slowly up on cities, but no player will.
Surely I have missed some options. So, what do you guys use for your armies when running Esus?
ps. I still need to explore the slave mechanic (I've been waiting a bit to see if it is tweaked, as people have posted about imbalance).