The Opera event is likely to be your first big hurdle. While Oz is fairly straightforward -- it's an add fight that you should approach the same way you did Moroes -- Big Bad Wolf and Romulo & Julianne are an almighty pain in the ass. Pray you get Oz.
Trash clear: I usually stealth past the Skeletal Ushers. The "actors" before the stage take about 3-5 minutes to clear, but don't pull too many at once, and make sure you yank them out of the spotlights they'll spawn. They still do a surprising amount of damage.
Kill: This depends entirely on the event you get. Oz can be done in about 3-4 minutes. R&J is usually around 5-7 minutes, but it'll be considerably longer if you make mistakes and let Julianne heal too much. On the sole occasion I've managed a Big Bad Wolf kill, it's a 10-minute fight.
Spec: Bear. Regardless of the event, you will need the survivability.
Gear: Bear. See above.
Romulo and Julianne: This can be tough because control of the fight depends on one of the things we're not that great with -- frequent, reliable interrupts. Julianne will, for obvious reasons, be your stumbling block to success. Romulo has a stacking poison effect that can be a worry, but with luck he'll be missing you too much for it to be a real concern.
Phase 1 is Julianne on her lonesome, and she can be taken from 100% to 0% fairly quickly in cat form (even while you're rocking bear gear). Maim every Eternal Affection without fail. You will be fairly low when she dies as you're not interrupting her other abilities, but you've got just enough time to heal up before Romulo spawns. Add an Abolish Poison to yourself if you can.
Phase 2 is Romulo. Go bear and take him down to 0%. He's a straight tank and spank, and the only ability of any concern is Poisoned Thrust. Romulo should die before this stacks too high; if not, you can survive popping out to slap another Abolish Poison on yourself.
Phase 3 is where things get tough, and the first thing you should do is /focus Julianne. Done that? OK, the secret of this fight is to keep her running. You can't afford to go cat for this, so your two options for interrupts are Bash and Feral Charge. If Bash is on cooldown, you should be kiting both her and Romulo around the stage. Where you kite doesn't particularly matter, because Julianne needs to stop in order to cast anything, which gives you early warning that a spell is on the way. If you're already in motion, you should quickly have the necessary range to Charge her. Again, don't worry about interrupting anything other than Eternal Affection. Interrupting that heal is your first priority, and just DPS both her and Romulo down slowly while you watch for it. Don't forget that they have to die within 10 seconds of each other.
Big Bad Wolf: Alaron at the Fluid Druid described soloing this better than I can. Be prepared for a very long and frustrating night if you get the Wolf. I have to confess that I usually give up after wiping to the damn dog for a fruitless hour and enlist help, but it is soloable.
Oz: Even in good gear, you'll probably have to blow some cooldowns on the early part of the fight with all 5 mobs on you. That said, Oz is by far the easiest among the Opera events to solo, and phase 1 is essentially Moroes + adds all over again. Once all of them are active, Berserk to get 1 or 2 of them down quickly, and after that the fight's a leisurely tank and spank. You can go cat full-time for the Crone when she spawns; just avoid the cyclone that paths (very slowly) around the stage.
- Earthsoul Leggings: Another early resto piece that was a recolored version of the rogue's Bloodfang set.
- Romulo's Poison Vial: This was a surprisingly good cat piece for a while, but good luck winning it over your raid's other melee or hunters.
- Ruby Slippers: This was a fun little item that could replace your hearthstone if you wanted, but they shared a cooldown. Boo on that.
Nightbane was once the terror of druid tanks everywhere due to his Bellowing Roar. For newer players unfamiliar with the mechanic, boss fears were among the many reasons that bears and paladins couldn't realistically be main tanks. If a boss feared you, they dropped aggro and then wandered off to start one-shotting other raid members for the length of the fear. You could get around this by keeping a Fear Ward rotation on a bear or pally tank, except: a). You needed priests: b). Only dwarf (and then in BC, draenei) priests had it, so: c). You were entirely at the mercy of these players' attention spans, and: d). If you were Horde, you were up the proverbial creek.
Whenever anybody complains about raiding being dumbed down and class abilities homogenized, I laugh and laugh.
Trash clear: Nightbane doesn't really have trash as such -- just a few Trapped Souls and Ghastly Haunts wandering around the entrance to the terrace. All can be stealthed past, or killed as you prefer. Budget about 4-5 minutes if you do clear them all.
Kill: He's still a respectably long fight; plan on spending 8-10 minutes. As an aside, you no longer need the Blackened Urn; you'll find a small urn in the middle of the terrace that can be right-clicked, summoning him.
Spec: Bear or cat.
Gear: Bear or cat.
How hard?: Even in the earliest of Wrath's epics, Nightbane no longer poses much of a threat. The only element of any real annoyance here is going to be Distracting Ash. Because you have plenty of time to pop out and heal during his air phases, you don't even need amazing gear to get him down. If you can survive one ground phase, you've got the fight in the bag.