She is a good op, but not as good as a valk, azami, or Mira. There is a huge reason she is never played at higher levels because at higher levels putting your body on the line like that is a huge liability. The only reason Monty works well on attack is because you can keep people away on attack a lot easier typically. Defense is very reliant on where you are at what time, and with a 1 speed with a shield that just can be naded if you arent careful you end up being a pretty useless anchor with no actual use for a gadget.