I have been on the side of both parties, so I may give a more detailed, less subjected opinion.
For me the tensions started growing during the yule 2014 event. I was in ancients back then, this was a time when we still were rolling on drops. I didn't mind back then, because if a fellow mage needed an item, we mostly borrowed items to each other, for example:
I got scammed big time and poisonous(alliance) borrowed me a comrak neck till I got my stuff back and tomtomtom(ancients) borrowed me alot of items and taught me alot about the mage class.
The system was flawed even back then, but we managed together to reduce those flaws as best as we could. Tensions started growing when some rumours were going around about this clan, spread by only two players( as far as I know). They said alliance were all transfers from epona, called them the 'eponavirus' or 'eponascum'. Basically all the clans in lugh were almost bullying alliance. They were scared of alliance, said they would take over the server. This is when a big rift got created. For example we used to server-kill aggy(lol). Alliance introduced a new policy. They did not include, but would also not exclude. What this meant was that they wouldnt call anyone when they would spot a boss, but they would still allow you to roll when you would arrive in time at that boss.
So basically the old lugh clans and alliance kept grewing apart from each other. Alliance members were forced to unfriend people outside alliance(according to rumours. I don't know if this is a fact). And if you were in an old lugh-clan and you were friends with someone in alliance you were marked as a traitor. This was a big problem for me, I had friends on both sides and it was hard for me to choose between them. I tried to help defend the system as long as possible till couldn't anymore. In the end, alliance tried to go dominant, but they could only keep this up for a few days. Then they rejoined the other clans again as it was before. Still alot of tensions.
Because of this, the remaining players of what was left of the old lugh-clans regrouped in a different clan called 'virus'. The purpose of virus was to counter alliance. They asked me to join as well. I did but I discovered soon that this was not the clan I thought it was. All they were talking about is how they would destroy alliance. I said I still had friends in alliance and I got kicked because of this. After this I made my own clan called 'Neutral'. I tried to stay neutral and treat my friends equally on both sides. Alliance appreciated this, the friends in virus disgusted me of this and branded me even more as a traitor.
Lugh still got tensions but it was doable, till virus locked mordris one day. A godly druid ring dropped. During dicing the lock group switched this godly druid ring for a mighty rogue ring. A few honest players like sabre for example tried to fix this whenshe discovered this. She made sure that all the druids were brought together again and that everyone had a fair chance on this drop. After this incident alot of players quit the game, alliance became by far the superior clan in lugh. I stayed a while in my own clan, but I became bored, I tried to join hobs and synergy, but they both rejected me. In the end I could join ascension, a neutral clan that consisted of tobius, lukov and me. After a while lukov and tobius went semi-inactive. I found myself alone again in a clan. I left ascension and joined syndicate, because it seemed active. When I joined a few players from syndicate went to alliance, so again I was almost alone in a clan. Then the summer event hit. I managed to win a full spirit set by myself in a week ish.
Then I got a message from an alliance member. He said that soon alliance would go dominant and abolish the dicing system. They told me other players from the other clans had the same choice. A few including me joined alliance, alot stayed to try counter alliance, mostly in vain.
The reason why I couldn't defend this system if because of the following reasons:
-Most of my friends on my side who truly believed in this system left the game. They d'rather give up fighting and solve things peacefully then use their hatred to fight. (I still play with some of them in clash of clans

)
-All what was left of the old-lughians were changed friends, only set on destroy on alliance. All they cared about was retaliation, because alliance destroyed their system. I saw my friends change, doing more horrible things till I hardly recognised the players I used to call friends.
My experience in alliance
Alliance is from the inside a very friendly tight-knit bunch that just wants to have fun. They care about each other and have each others back. On contrary of the dicing system, everyone has a fair chance on gear, based on efffort, not just some luck.
I do understands everyone frustration though, or at least most them. I still speak with alot of players outside alliance and I know alot want to join alliance, but they are either scared of public opinion, scared that they will get rejected by alliance or they do want to join, but are loyal to friends that are too stubborn to give in.
Thanks if you bothered to read this all. I hope for the newer players that this will give a bit more perspective in the current situation. Ofcourse I probably have missed some things. Feel free to add anything to the story as as its factual.