Certain engine core components being rewritten due to horrendous performance issues in various subsystems were done.
Trion has stated multiple times that RIFT was built using Gamebryo engine. I wouldn't imagine them lying about not having their own engine for the game.
I agree that not having source access to the client is a big disadvantage to using Unity for a game like this.
The ability to do so fairly directly is a big advantage Gamebryo has over other game engines such as Unity.
No it isn't an opinion in the least. The core renderer is nearly replaced in every game using it, the scene graph is cache miss heaven and the old way of doing things which doesn't scale with hardware, there is virtually no multithreading due to not having a job proper system. Also note that as I mentioned BigWorld and Hero Engine are proven solutions.. just because you don't like the gameplay or design decisions it rarely has to do with the engine.
As for the architecture being "old and stale", this is an opinion. If I were investing millions into a game, I'd definitely prefer a traditional and proven approach rather than a radical and risky one especially for a game engine. If the company wants to take more risks, they should develop their own engine in favor of unproven solutions.
You can also write extensions in C++ without a source license if you run into scripting performance issues. Also controls and gameplay in SWTOR are design decisions you could easily clone WoW or RIFT with it if you chose to do so.
By "too managed", I mean the scripting language seems like very high level code in contrast to a much lower level language like C++. The reason I said "seems", was because I haven't played around with it much, but I have played SWTOR for awhile and in my opinion the controls and overall gameplay is quite clunky compared to games like WoW or RIFT.
You could just as easily cross-compile a native desktop application if you wanted to. Not to mention there is no 64 player limit unless you are going to use the default Unity networking subsystem... which they will even recommend you not to use and to go with Photon, Smartfox, etc.
Unity is a good engine for browser clients. That's about as far as it goes from what I've seen. Both examples you cited only use Unity for their browser client. In my opinion, if you're going to have 64+ players visible in one area, you're heavily limiting your performance by forcing players to use a web browser.
AAA is commonly known as big budget titles and has nothing to do with whether you like the game or it was a flop commercially.
Your definition of AAA is very different from mine.
Then you've never looked at the source... the amount of work needed to modify the networking subsystem is extremely substantial. Ask anyone who has worked with UE3 how fun it would be decoupling the networking and building a new system. Sure it definitely has been done before but the amount of work is staggering. At the same time the OP isn't asking for a 6-7 figure engine... which you would need since you couldn't do it with UDK alone.
You're right about UE3, but I would still prefer it over Big World or Unity for developing non-browser clients due to the quality of the engine coupled with the successes of RPG games using it.
Not at all, Big World and Hero Engine are the enterprise level solutions that come boxed and ready to go without extremely heavy modifications.
You seem bias against enterprise-level solutions in this discussion.
Completely your own opinion once again. Companies like BigPoint, EA, Cartoon Network, etc have large budgets and have put together some great games using Unity. None of them are "browser ports" but that is their target. If they wanted to they could have distributed Windows and Mac binaries by cross compiling.
No development company with a large enough budget to make a decent MMORPG is going to use Unity for an MMO as anything other than a browser port.
It's already been done multiple times.
Unity is great for many genres of games, but MMORPGs doesn't seem to be one of them. I'm not implying that it's impossible to make a multi-platform MMORPG in Unity, but it's definitely unreasonable.
Also for the record I've actually worked with GameBryo, UE3, Unity, Reality, and have worked on more than a few custom engines.