I won't touch the toppic of real life combat as this is a video game and I don't care how much the devs of any video game depart from real combat physics to make a game fun.
But related to in game mechanics dagger+shield looks very good on papper but requires a little more resources than it would for a regular tank but for a pvp setting, the amount of tricks you can put on a dagger+shield user are very hard to gauge and could be seen as a game changer,if used right.
