AFAIK, the tyranid focus depends on the control of the race, not of specific guilds within it. However, I agree. As guilds / groups of players, there's almost always a problem with reward which encourages whack-a-keep behaviour that delivers greater benefits to the individual while contributing rock all to their wider faction. Of course, giving too much reward for staying put leads to the reverse. And giving no direct reward for either would encourage people to not bother attacking defended positions, but seek out skirmish and open field combat. Its a royal pain in the rear to balance, with no perfect answer, and why its useful to look at how other mass open PvP games have attempted to handle this to get a feeling for the strengths and flaws of different approaches.