This seems an odd topic.
It is not Greedy to want to have your time rewarded.
It is Charitable to give to those in need.
It is not one is -1 the other is +1. It is more along the lines of one is 0 the other is +1.
Everyone put effort into a instance, everyone should have EQUAL chance for reward. If one person wants to give up his chance so another can have them - it makes them charitable. It doens't make the person who wants their JUST reward evil or even greedy. The self-entitlement some display is fairly overblown.
As for the Tank being the leader of the party. While that is common it is hardly always true. And tanks shoudn't always be the one pulling all the mobs. Taunt leaves them open for a second or so. Depending on the number of mobs they can get stagged killed pretty easily. It is better for someone with invulnerability frame to do the pulling, and clumping, so the lancer can then take over aggro. Hell sometimes even the priest in the static can do it better than lancer.
Though I been away for 3 month so things may have changed. Maybe they patched in more invulnerability frame for everyone. But roles should adopt to the sitation. The leader of the party should always be the one who can dish out correct tactics and allow individuals to work as a group. It should never be based on character class. Sometimes as Lancer I can't even have time to type out instructions, so I give the organizational role to the healers. Since they have better view of the whole map - instead of just the tummy of the boss.