though I'll most likely abstain from everyone except Froslass and Moltres, just because I haven't used any of the others ones enough, here is my opinion,
Cresselia: As Franky mentioned, although I've grown to adapt to Cresselia, she is still too tough to take out. Though the Sub/CM/Two attacks is extremely annoying, she can wall pretty much any physical or special (depending on how you EV it) attacker and start spamming toxic/thunder wave with ease. What makes her even more difficult to take down is the fact that she has Levitate, making her immune to Spikes, which is a huge part of the metagame. That's why I feel she is BL.
Froslass: Without a doubt, BL. The ease at which she can get down 2-3 layers of spikes is just ridiculous. What makes her the best spiker is that she can't be spun on. Suicidelass means that something is going to die thanks to Destiny Bond, and Bulkylass means that she is sticking around for a long time, making her a reliable spin blocker as well as spike stacker. None of the spinners can really threaten her and the most used spinner, Donphan, is threatened by Ice Beam. Froslass even makes other pokemon more broken, especially Moltres, who can OHKO/2HKO anything with Spikes support. Simply put, she needs to go.
Porygon-Z: I think the set that makes it BL is the Choice Scarf set. As long as you aren't retarded and just spam Tri-Attack for everything, the Scarf set can be deadly. It's just too damn powerful. The Nasty Plot set is good, but more manageable than the scarf set because although it is quite fast for UU, there are a lot of of things that can outspeed/revenge it. Overall though, I'd say it is BL.
Raikou: I'm still not 100% sure on this one, but as of now, I would probably vote Raikou BL. The difference between Raikou and Cressy is its speed and potential of it being an immediate threat. Though it isn't used very much, I think a very dangerous Raikou set is the LO CM set, simply because of the threat it poses after just one Calm Mind. However, for any set, Raikou can easily wear down its counters to the point to where they can't counter it anymore, and then its pretty much good game. It's also bulky enough to take quite a few hits. For these reasons, I think Raikou is BL.
Moltres: I think Moltres with the right support is BL. You cant just throw Moltres on a team and expect it to do well. Froslass is a big reason why Moltres is such a huge threat, but even without it, Moltres can do a shit ton of damage to the whole metagame. Yes, the stealth rock weakness is unsettling, but with rapid spin support, Moltres is extremely hard to take down thanks to her bulk, and can KO everything in the process.
Damp Rock: I honestly, don't know as of now. I previously thought it was UU, but as of late, I've seen how destructive it can be. For now, I'm going to hold off on deciding.