No such thing as best class. Each have their pros and cons.

All classes are able to solo elite Rahab with the right gears and build.
Even warrior class can do it. (Proof: https://youtu.be/5zdUzNGZlTk)

But if you are looking to do the most damage (without ult), then go for rogue.

[PS: Mage (fun class/jack of all trades) and warrior (survivability A+) can still do decent damage, but not as much as fully decked rogue (glass cannon)].