This is by far the biggest and most competitive wotlk pvp private server as far as I know. Very alive, you can always find games and bg's, any time of the day.
You won't have to do any raids, in fact, you can't, as there are no mobs on the entire world map. You start with full relentless gear and can already buy the wrathful offparts without any rating required. Gear is bought with honor points or arena points, to be earned in bg's and arenas. It doesn't take very long to collect the full gear. Also, there is a templace NPC that automatically sets your talents, glyphs and starter gear so it saves you some time if you just want to look around (of course you can adjust your gear and talents at any time).
You mention class balance. This server is in the original 3.3.5a balance patch. However, the gear goes up until item level 284, with practically all warriors at higher ratings carrying Shadowmourne. At the highest level, the warrior class dominates the 2v2 ladder, as they scale insanely well with this gear. (I only play 2v2 so I can't say anything about 3v3).
In my opinion, they should put the highest attainable item level at 264 instead of 284, I think that makes it more balanced. But apart from that, I think this is a fantastic server. There is even a spectator NPC that lets you spectate other player's arena games, and it also lets you replay older games, including your own, which gives the opportunity for you to analyse games and come up with new strategies.