The winners are the two allies that acquired 80% of villas of top 10 tribes (which is usually at least 75% of active player villas).
I can understand why they wanted the world to end already, W3 started sucking by the time we had 70% of the top ten player villas. Suddenly all our enemies went inactive except for a few barb munchers in the backlines, but there were so many villas that it still took us a month and a half of inactive munching before we finally ended the damn world. There were no fun fights, it was just a miserable trudge of coin nobles and send them out. I didn't even queue up units for the last 3 weeks of the world.
This is the end game setup we have right now. THIS is the problem, not tribes merging, that's just diplomacy in action.
Also, this rule is ridiculous because any tribe who merged before it was made suddenly has an advantage over tribes that were planning/about to merge. If it's going to be a rule, it should be a rule AT THE START OF THE WORLD, not halfway through.