Regarding C8 and narcades... I've had the best luck with them when jumping over a mech to get behind him, and chucking it right after I spin 180 and am starting to pass to his rear. Just point the reticle at the middle of the mech and lob it. In most situations it will stick. If you're aiming for legs... probably not gonna happen. Best bet is to run a game local on your PC and practice a bit to get the hang of it.
Not saying they don't bounce off from time to time.... but they're cheap, so if you're running dedicated BA, throw all them suckers before you get popped... Quantity = quality =) Not to mention if you miss in a big mess-o-mech-melee, someone will probably step on it anyways. Random explosions are good!
Infernades! Yes these will kill you pretty quick... I think they have less than a 3 second timer, and a large blast radius. Trick is to chuck it as you're starting your jump BACKWARDS, or are at a high enough height moving in the other direction. They may generate a nice flash of heat to mechs... but killing other BA are their speciality soley on their quick fuse and large blast radius. I finally got a clean kill with one the other night and it felt good =)
If you're playing BA, your job isn't to have the best K/D ratio... it's to sow chaos in the enemy's ranks. Little mechinized suicide gremlins!
All in all, they're still not where they should be, but they seem to be working better than they were in 0.2.0