You're right the only ones I find useful are the SCAR, SCARAB, Feline and Jackal. Bit bored of using them.
The rest are mostly useable, some are not, but if you use them it's difficult to compete with the fully-auto's (spray and prayers). I don't care who you are, if you try secondary-only you are not going to do well, what I mean by well is 2 KD+ in TIA and IA. The four above weapons will own you even if they are bad players.
They only need to look at you press and hold LT then hold RT and your finished. No skill involved, aim assist is too helpful.
I mentioned this in my below thread.
http://www.gamesas.com/forums/viewtopic.php?f=41&t=23395
I wish they buffed the secondary's. I'm in two-minds about having snipers as OHK, 2-hit kill imo is practically useless while OHK is overpowered.