I think a tribe can be perfect if it consist of players that know each other, and that they can keep contact to each other via cell phone, messenger plus other internet tools.
And if most tribe members are really addict to this game and can always sit in the front of PC at least 12 hours per day, plus they can last the interest till the end. But i think nowadays most players of the newer generation will not commit to such addictive playing style where they are willing to even log in their account via cell phone, laptop etc where ever they stay. And most older generation players stay in the older world to continue the battle, so there aren't much veterans to lead a tribe in the new worlds unless they lose a war else where.
One example is that the mass quitting of CLOROX in W8 and then merrick2 brought them over to W37 to start Insane which is doing pretty well since they already know each other from the beginning