I second Lethal. RS is really the only MMO where you can literally do anything and aren't really tied to a class.
As far as the classic "MMO Styled combat", I don't think you're going to be able to find anything that compares to WoW.
Some fun alternatives that have a bit of a different combat system, while still being solid MMO's would definitely be Guild Wars 2, and Black Desert Online. These both have an upfront cost, but don't have a monthly subscription like WoW and RS have.
If you're looking for a completely free game, I'd suggest taking a look into Blade and Soul, or Tera. Both are a ton of fun, but have their shortcomings when comparing them to the games I brought up before.