Back to my original home. Need some questions answered.

Hi,

After jumping around on other servers, facedesking and a lot of sigh'ing, I've decided to return to my original WoW home, which is where I've spent most of my time playing in the past.

I see a lot has changed, even the name of the server. I lost my characters and stuff so I need some info on the "Start from scratch" topic.

What's the state of the expansions? I expect MOP to messy atleast. And WOTLK to be quite scripted.
Recommend me a realm.
Tell me which classes are too bugged to bother with them (I remeber some old bugs of the original molten, before 2012, where hunter and warlock pets would not scale off master's stats)

Thanks to anyone who can answer me.