Since the subject hasn't been raised for quite some time, I'm curious to know what (if any) Major Overhaul Mods are being used by members of the Rome 2 Heaven community?
I've personally been a player and supporter of Divide et Impera almost since it's creation, and from what I can tell it's become the Major Overhaul Mod of choice by a large portion of the Rome 2 player base. Version 0.85 of DeI was released yesterday morning and brought with it several faction and gameplay overhauls, including a revamp of army and navy stances. Thought the DeI team might not adhere to 100% historical accuracy, I believe they've created the perfect balance between historical authenticity and enjoyable gameplay with their mod.

The only beef I have with DeI is the provinces they give Carthage in the beginning. I have both Radious and DeI in my mod workshop thing, but I've been preferring to use a conglomeration of mods to my tastes.
Only thing I do have to say about DeI is that the battles are fantastic! They last much longer, and it's more of a sudden break rather than a drawn out piecemeal battle. I remember one battle I had with the Turdetani as Cartahge where it seemed I might actually lose, as they had good morale left, and were chopping away at my guys to the point where they were killing faster than being killed. Then suddenly the Turdetani break, seemingly all at once. I suffered many casualties in that battle, but it was a very fun one!

In the early days of Rome 2 modding, Radious' works were definitely my mods of choice. However, I eventually grew bored with all the 'fantasy units' he added and moved on to Magnar's mod. Magnar's reminded me a lot of Europa Barbarorum with it's focus on historical accuracy even at the cost of gameplay balance so I played it for quite some time. What pulled me away from it however, wasn't DeI itself but two modders whose works I'd been enjoying and following for quite some time: Dresden and Epaminondas The 'Oblique'.
Dresden had taken charge of the 'Traits, Talents and Toadies' mod after Hellbent resigned from modding so I'd been following his progress with this and his Hegemonia and Turn Per Year mods, while I'd been enjoying Epaminondas' 'Ancient Colors'. When both of them announced they'd be working together along with Selea (creator of the Ars Gratia Artis mod) on a new project called 'Divide et Impera', I immediately became interested and started following and supporting their new endeavor and the rest is history.
*****
To focus back on DeI itself, the battles are indeed one of my favorite parts. I was fighting a battle against the Persians as the Seleucids in one game and out of all the battles I've fought since I bought this game it's still my all-time favorite one (so far). I was outnumbered roughly 2-to-1 by the Persians whose army was mainly comprised of spearmen, hillmen with assorted light infantry and a few squads of Medean cavalry, while my army was based around a core of phalangites supported by hillmen on the flanks with 3 units of Medean cavalry and my general's Cataphract Elephant guard. The battle started fairly by the book with my phalangites pinning the enemy infantry in place, while my cavalry countered the enemy's but halfway through disaster struck.
One of the units of hillmen guarding the left flank of my phalanx line suddenly broke and began fleeing from the battle. Hillmen already have poor morale so when the other units saw one group running for the hills they soon followed suit. Instead of chasing after the routers, the AI sent its infantry charging straight into the exposed flank of my phalangites who managed to hold but were in dire peril. I would usually send my general to shore up such a calamitous break, but he was already busy countering the Persian cavalry on the right flank and I knew if I pulled him, and the morale boost from his presence, away that my hillmen there would break and the disaster would only repeat itself. With no other real options left, I decided to focus him and all my attention on routing the left flank of the Persian army before my own left could collapse anymore.
The rest of the battle played out as a nail-biting see-saw with some of my phalangites breaking and routing from the field, but thanks to my general's elephants (and some touch and go charging with my cavalry) I emerged triumphant though it was a somewhat Pyrrhic Victory.

Elephants are definitely a battle saver, as they are more than slightly over powered lol. In one of my HatG battles, I created a general in Gadir (I think it's called Gades in game) to save said town from the Turdetani which had recently declared war. Of the 1200 or so Iberians deployed against me, 500 and some change were killed by my elephant general alone. Granted, many of the Iberians were slingers/javelinmen and lightly armored infantry that can't hold back an elephant charge, but still

They can definitely be game changers if used at the right time and place, but they can also be countered fairly easily if you know the right tactics or the enemy commits them too soon. When I have them, I use them mainly to counter cavalry and only send them charging into infantry if they have a clear shot at their flanks & rear or if they're exhausted and vulnerable to morale shocks. The thing that lets them rack a high kill rate is that they get what I call a 'death area' around them when they're chasing shattered or routing units. I'm guessing CA gave them this to simulate how elephants would easily stomp anything that got in their way to death, especially a helpless person fleeing for their life
Against them, I mainly stick to the tactics I used in EB: pelt them with hundreds of arrows, javelins and stones until they're all dead or they run amok.

Been busy the past couple weeks so I haven't had much time to play or post as I used to
Started an Epirus campaign in DeI. Because Epirus' diplomatic penalty, I had to start things slow and limit my conquests to Greece and the area surrounding the Aegean and Adriatic. I focused mainly on the war with Sparta until Athens decided to butt in. I was outnumbered in several battles and managed to win them all, but because of DeI's tweaks to replenishment (and a submod that nerfs it even more) I wasn't able to follow up and conquer Athens and Sparta themselves until I'd wiped out all their armies and given my troops time to replenish and reinforce.
Once Athens and Sparta were out of the way I went after Knossos and made Crete a part of the glorious Kingdom of Epirus. I had then just began to rest on my laurels when Rome declared war on me. So far I have southern Italy under my control and took Rome itself on my last turn. The Romans responded by offering a peace treaty and 32,000 talents, but I refused and chose to persecute the war to it bloody and inevitable end

Sounds terribly interesting.
Meanwhile, I have been searching for mods which significantly alter the dynamics of campaign map gameplay in new different ways. Either the ideas I have in my head are highly difficulty, unsought of yet, or just not inspiring to those who mod Rome II. I shall have to try and break past the initial clueless factor that shall come with trying to do it myself, for it is gnawing at my soul like an Undead Hollow.

*bump*
So in the past 9 months there have been many new overhaul mods that have sprung into development, and many of the past ones (such as DeI and Radious) have evolved and improved even more.
I've been playing a Macedon/Antigonidai campaign in Divide et Impera 1.0, which was released just before the turn of the New Year and I'm simply amazed at what the DeI team have done with their mod. Field battles have been completely rebalanced and siege battles have also been improved greatly with deployables for defenders and the AI now taking time to build siege equipment, wear down and even starve out cities instead of attacking right from the start and using torches to burn their way into a city.
Economics and army maintenance have been tweaked so that no one (including the player) fields the max number of full stack armies all the time, and the loss of even one army can be a crippling blow for a faction that can leave them extremely vulnerable until they can raise a new one. Politics have also been tweaked so that your faction leader can have a global effect on your whole empire if he's stationed in the capital and players can reach a sweet spot that can keep their faction's ruling family in power without making civil war a certainty. The benefits from political ranks achieved by ruling family members also stack so that a fully promoted family member can greatly increase the order and efficiency of your empire and losing such a person in battle or to political intrigue can be a devastating blow to your dynasty that can change the balance of power against you.
All in all, I highly recommend Divide et Impera 1.0 and all its following versions to any Rome 2 player who's looking to play a more historically authentic and immersive gaming experience with Total War: Rome II.