I have always played melee characters, just can't get excited about magic I guess.

I boxed a Bruiser, Swashbuckler and Warden and then added a Dirge as I had a free 85 character.
3 Boxing with Mercs was very viable and it was nice and less complicated than 4. My chars are only 91 at the moment so haven't reached end game content. The instance bosses are starting to get trickier though and much harder to box as they aren't straight tank'n'spank. You need to do various things with chars at the same time which makes it more difficult. Mercs actaully help here as they just keep healing or bashing away.

I have always used the Chains of Eternity collectors edition Templar merc as my main healing merc to backup the Warden. Krivox is amazing and the Warden mostly just DPS now with some group heals or cures when needed.