In order to increase the chances of us getting legendary armour, we need to farm both vanguard and crucible marks. The best way to do this is to run through heroic strike games with appropriate bounties, and the same goes for crucible games. If you get some crucible bounties for completing 5 control matches, try to get some that say kill x titans or kills with melee ect. Doing firefight teams also work well as we can support each other and see who does what well and can evaluate who would work well with who. This way I think would be the most effective to farm legendary armour.