Just remember that while a rifle can double as a club, a club wont double as a rifle. Only the toughest threats need to be engaged up close, everything else is blaster fodder...and having a melee weapon means you'll HAVE to get in close to do ANYTHING. Having that rifle means you can charge in guns blazing, grabbing the attention of everything in the room while choosing the most strategic location to bring your other tools to bear on the enemies. On the flipside, a jedi is going to have much more trouble with positioning, simply because outside of that lightsaber's reach...they aren't quite as threatening. Given that a trooper wont have the force to fall back on, as a consular would, but will have tools to even the game up close...well, it makes sense to be a threat from every position. This is how I choose to justify it to myself, a vanguard is prepared for EVERY situation, rather than trying to adapt every situation to their ideal.