The last one was about an hour ago, actually. When they brought the servers back down after the short-lived startup. You can see it for yourself at where it says "1hr" under the bit where it keeps track of how long it's been since things were posted.

It really does come down to playstyle, ability, and preference. My guild routinely runs HM 55 ops, and I find my merc and our sniper bouncing back and forth in parses. It really comes down to how often our abilities proc. Yes, the maximum potential DPS of snipers is higher than the maximum potential DPS of a merc, but that's only if both are standing perfectly still. Add pretty much any operation mechanic, and you'll see snipers take more of a hit than mercs and you land about even. That said, Snipers will be the better choice for easy damage. If you want to max out Merc DPS it takes a lot more concentration and precision.