Let's be honest here for just a second. The melee system right now needs a complete rework. Exterminatus mode in Space Marine was bad enough for Assaults that didn't have good latency and there was no stamina system to prevent you from swinging until you died. With Sure Strike and a Zeal perk you were a melee combat monster against anything except black armor Orks and even then they required a very specific attack rotation in a one on one. You lacked Impenetrable so were vulnerable to ground fire. With a hammer, Sure Strike and Impenetrable you could effectively fight everything but had to be smart about your positioning and overhead stun and swing timing. But all of this was reliant on decent latency. The current stamina system will ensure that it'll be teams of dedicated trigger pullers and nothing else because melee as it is now will not be combat efficient against swarms.
Gotta point out the same as Bob; Current melee is insufficient for prolonged fights with the Tyranids that are confirmed so far to be melee dedicated. THQ;s SM had plenty of AOE stuns with little limitations / cooldowns. Here I can think of only jump pack landing and a defensive kick.
If you're in prolonged melee with the Tyranids, you're probably doing it wrong. That is, after all, the area where they are rather terrifyingly dominant. A balance point where player melee characters have the opportunity to step in and temporarily stem or turn back the tide, but can't sustain the situation and need to pull back sounds like a good one. Theoretically speaking, that might mean heavy weapons bearers mowing down the Tyranids rushing their position until they have to reload, with melee characters holding back the swarm long enough for the heavies to get back in action, and those carrying medium weapons plugging the inevitable gaps that the others won't be able to cover. And everyone pointing at the dude with a plasma rifle and calling him a dick*. *Until the first Lictor is sighted...
