On the nades: It's the old gameplay > realism thing. Sure, it doesn't make sense to only get one and no more until you die. But they're so freaking strong that if you could load up on them then just about any alien chamber would be worthless, falling to nadespam. That's why the GL has a higher cost, and makes the wielder pretty vulnerable, unless they want to GL their feet to take out skulks.
On the focus: Yes, now that the novelty is wearing off, I begin to realize that it's about worthless. Against a lone marine, sure it's fun to run up behind him and chomp him in one hit... but if you can't kill a lone armor 0 marine from behind anyway, there's a problem. And when chomping buildings... it should AT LEAST do an equal amount of damage over time as unfocused biting, if not more. It's like focus is the counter for itself... everything good it gives you, it gives something bad back in return. This is the ability that will save sensory from being the last ridiculed chamber?
And as far as res whores/res hoarders/whatever you call them: It's the many and obvious bad people who have given the few good ones a bad name here. When someone jumps in, drops no RTs, doesn't save for hive, doesn't even drop a chamber, goes fade/onos ASAP and then whines that no one will drop him DCs/MCs, only to die thirty seconds later and then LEAVE THE GAME... well, that's where the animosity comes from, and it happens far too often. If someone says right off 'guys, I'm a very good fade, if I fade early I'll probably last for the rest of the game, and I'll keep marines distracted and take out elec'ed RTs' and so forth, THAT'S GREAT. Hoard that res buddy, you'll be helping the team.
This is why civilian always has an open pass to save for fade, or why LB gets to save for onos without complaints (preemptive: it's not just because it's his server olo bant omg). They're just really GOOD at it, and they help the team a lot.