>>493489207First off, killing a Hive Tyrant absolutely doesn't have this effect on entire planet. Some nearby Tyranids might die from the shock but overall all you'd be achieving is them losing a lot of coordination for a period of time before the Tyrant is reborn (their minds don't die, just their bodies).
Hell, it's even a plot point in some book that one a Tyrant is slain nearby Tyranids go berserk in effort to kill whoever killed the Tyrant so they don't live to share the experience and weak points of one with others. There has to be Tyranids to go berserk, if they're all dead they can't go berserk.
Also, killing a Norn Queen isn't a perfect solution - killing a Norn Queen is how you get multiple Norn Queens to replace it and form splinter fleets, you literally have to destroy a chunk of Tyranid biomass the size of a planet to make sure nothing shows up again from that tendril apart from ferals. Tyranids aren't a problem just because there's a lot of them, they're a problem because there, in fact, isn't some singular threat Marines can just assasinate and be done with it forever. It buys time, sure, but all you're doing is delaying an enemy who fucking loves attrition warfare.
