Ramming was used in the U.S. Civil War. The CSS Virginia's first target in the Battle of Hampton Roads, the USS Cumberland, fell victim to the Virginia's ramming prow after receiving her close-range cannon-fire. The prow was damaged and ripped off as the Virginia extricated itself following the ramming maneuver. The Cumberland sank, and the Virginia continued to wreak havoc on the rest of the small US squadron anchored nearby, though it had developed a leak in the bow.
Whether or not ramming was used that often, the fact was that it remained a potential threat in close-quarters naval battles, enough so to influence the design of US Navy battleships to include ramming prows or ram-worthy bows. During Admiral Callaghan's night cruiser action vs. Japanese surface ships, the combatants crept so close together before the shooting started that ramming could indeed have been tried, had a commander on either side of that engagement chosen to commit to that option. That particular battle was so chaotic, however, that no one could say for sure whose ships were whose, and after several sinkings, horrific shellings, and friendly-fire incidents, most captains present were more interested in ending that brutal and confused engagement rather than kick things up a notch with ramming techniques.
As far as World of Warships is concerned, yes, it is a very valid tactic. It is kind of a [edited]move (at least in the eyes of the recipient ;-) ), but valid and well in line with doing whatever it takes to get the job done. Twice I've used my Cleveland to ram and sink an enemy battleship (a mostly-full-health Warspite trying to creep by itself into the friendly CV's area of the map, and a mostly-full-health New Mexico defending its cap point against my teammate's DD whilst ignoring my presence a few moments too long), and trading a light cruiser for an enemy battleship is both a brilliant way to end your match, and a potential game-changer. You have to be in a frame of mind that's willing to instantly dismiss caution and self-preservation and take one for the team when an opportunity for ramming and eliminating a nearby goliath presents itself... but you also have to be on a potential collision-course vector already, and must have an idea of how to steer so as to cause a collision against a potentially resisting foe... If battleships don't want to die from 'outdated' ramming tactics, then they should learn to sail in well-maintained battle formations for protection against killer-Clevelands. :-D
