Out of 3 functioning tbc servers, people could argue that warmane's developers are in possession of the most advanced one in terms of raid scripting, spell interaction and class specific mechanics. yet, as it's becoming more and more visibile now, players are leaving to try uncertain projects that will most likely turn into a costly time sink.
and why exactly does that happen? for what reason would anyone leave the most stable server with proven longetivity, considerably high population and competent admins whose formula had already shown that you can create environment with shop features and fully accesible content that attracts thousands, gives you lots of fun and can be enjoyed endlessly, while requiring less commitment than ever?
well, if you listen closely to the voice of playerbase, you can hear about plenty of those, each person adding their slightly modified own. but just because there's a reasoning, it doesn't necessarily mean it's a rightful one. if by now a thought involving warglaives crossed your mind, you should sit down and realize that you're indecently clueless.
the root of the problem, I assure you, lies in a fundamental structure of character progression on outland. namely, T5 25man raids, that should be viewed as a link-up between the freshly started and already established ones are heavily overtuned, to a point where you are required to bring at least few people who are tier/tier and a half above it in order to stand a chance of killing anything inside those instances (disregarding fathom lord karathress and voidreaver). this affects everyone. end-game guilds die out cause there's no pool of raiders they can choose from if their rosters fall apart/fail to deliver. progressing guilds stumble upon a big obstacle, members start questioning each other leading to conflicts, as the memory of clearing the same content without a hassle is still prevalent. freelancers can not organize vashj/kaelthas runs to give t6/t6.5 players alternative from doing the same raids over and over again thus keeping them engaged in all that expansion has to offer.
the chain of issues expands deeper, general pattern remains the same. i'm not the first person to point out that the solution is rather simple. whether you implement it or add a global announcement that advises skipping T5 and going straight into hyjal is only up to you.