Please... 4.3.4 did not kill the server. If anything there were more people playing across all the Cataclysm realms during that patch than ever before. f I've said this once and I'll say it again, the reason Cataclysm is in this state is because it did NOT get the attention it deserved from Warmane past the Dragon Soul release. A few months of tweaks and fixes after DS HC was released and then stuff started to get bugged and people got fed up of it, the reason for Cataclysm being as it is is negligence.
The argument is always that "WOTLK and TBC have a greater presence in the Private Server community" therefore its what people want to play. The only reason for your WOTLK and TBC servers having more population is because they're basically nearly complete in terms of content and the only reason for this is because they've been around for such a LONG time that its simple af to script and the 'know-how' is there. That was NEVER the case with Cataclysm. The same holds true for other expansions. I guarantee if the same effort was put into Cataclysm that was done with your WOTLK servers, you would 100% see the population return.
You cannot blame players for leaving for Hagara not resetting, Bethtilac oneshotting players, no fully working CATACLYSM zones, drakes to zonozz and yorsahj pulling the boss and wiping raids, spine of deathwing not working at all now, Therazane reputation only worked in 4.0.6 and was fixed only RECENTLY, lack of older content, the promise of Tol Barad (omegalul). I could go on and on.
Point of FACT, neglect the expansion and people will leave. Fix it and they will come back. The wipe and refund makes no ****ing sense if it's gonna be you dancing around the issues on a clean server. If you DO decide to wipe it you gotta give the players that spent time on that server some sort of transfer option or compensation because we did not spend years playing there for nothing.
Put the effort back into Cataclysm, put Molten/Warmane's name behind it and people will back you and play here it will become even more profitable than it was before. Don't give us the excuse that it's "harder to port to" and "harder to work with". Having this expansion will set you apart from the others because nobody has a fully working Cata server and there are people that want it.