1 hand + shield teaches you to be a lazy player imo. Don't worry about how OP or UP something is though, if you have to manually block you will learn positioning, team fighting, fighting outnumbered, fighting ranged etc faster than someone who uses a shield. Whether something is OP or not is hard to call though and depends on a lot of circumstances.
Personally I feel EU1 meta has favoured shielders for a long time, but people resist against the meta because it makes the game more bland. People play M&B for the unique combat mechanics, and its like removing one of the key features to use a shield. The recent buffs were totally unneeded, but balance in cRPG has always been one the dev's weak points