I thought I might start an installment of hard mode guides, mostly for 10 man, but also for any 25 mans I have experience with as well. We are currently just working on Firefighter in 10 man for a new 310% speed mount.
The best part of 4T FL is that you have significant less trash to clear, always a plus on a fight, which after having done it on 10 and 25 man on at least 1 character every week since Ulduar was released has become at least an annoyance.
Knock down the towers along your way that spawn adds. For trash, you can take whatever you want, but keep in mind in the end you are going to want to use 2 siege engines, 2 demo's, and 1 bike -- but that only adds up to 9 people right? We'll, I'm getting to that, but for now just have the extra person grab a bike and ride to FL.
The general strategy here is to keep the demo's pyrite stack rolling (Keeping those 2 stacks rolling does an insane amount of damage). Of course, there are problems here -- ice blocks, Freya's adds, fire rings, and demo's being targeted. At least there is no longer a slowing debuff, it used to be worse! And lets not forget that he used to have more health.
Ok, so you are sitting there looking at the last bit of trash before FL enters the arena and you start the encounter. You will want to pull them individually, not at all at once, the goal being to leave one big guy up for now so FL doesn't engage. When you get there, gunners with anti air guns need to start filling the area with pyrite barrels. During this stage, drop the your boy out of the extra bike (someone you are comfortable with going onto FL to cause an overload (I'm going to assume you know how to do this, mostly because I'm already an ass -- pop cool downs, blow bloodlust/heroism, whatev), generally ranged dps on 10 man since damage isn't as intense as on 25 man) and have a demo passenger (whoever else is going up) load themselves to be shot out. The person who dropped the bike is going to become that demo's new passenger.
Time for some positioning: We want to have a demo on each side by where the pyrite barrels are hopefully collecting. See pic at the top, since I'm a nub to blogging and can't figure out how to pull it down here.
Ok, now that the area is littered with pyrite, and one demo has someone loaded in the man cannon, its time to finish off the last of the trash. As soon as FL comes out and targets someone the man cannon should be shot, launching the person onto FL to begin work on an overload. Make sure you are close enough, I've been shot short plenty of times. I can assure you its not funny after the 3rd or 4th time. Also, make sure FL has someone targeted or else the chain wont pull the person shot on top of him.
So now, one person is on top, working on an overload. The goal is for the demo's to get there stacks to 10 asap with the pyrite while their passengers grab pyrite to keep the demo's full and continually shoot more down. Gunners in the siege engines should be using the cannon on any adds that show up, or else shooting down pyrite. I don't know if you're getting this, but its all about the rolling pyrite, everything else is insignificant in comparison. The bike's only job in this is to throw down oil to help keep add's kited and to pick up the person who causes an overload. There is no dropping of tar in front of FL like the days of old, mostly because normally the bike ends up taking more damage then any it will cause.
Ok, you got an overload, now comes one of the tricky parts. One of the demo's will be throwing a passenger up eventually, until he is ready, the bike needs to pick the person coming off of FL, and hold onto him. This part doesn't necessarily require verbal communication, but it would help if you quiet bastards would talk in vent! Since you can't shoot pyrite with a passenger loaded into a demo, the demo driver is going to have to shoot pyrite as he comes back online, then his passenger will load and get shot up immediately so his stack doesn't stop rolling. The bike passenger will hope into the demo without a passenger now. That's all there is to the tricky switch.
Oh, except that you have to do this with Freya's adds up and running around, Hodir's Ice Beams, and the fire ring that does a decent amount of damage if you go into/through it. If you can keep this rotation up, and your stacks rolling, the encounter takes almost no time at all.
Note to demo drivers: You are eventually going to get targeted, the best way to handle this is to shoot your pyrite, turn around and sprint, turn back and cast pyrite quickly, then drive away from him again as soon as you do. Before your stack falls off he should be done kiting you and moved on like a sucka. Make sure your passenger knows whats going on.
Alright, since this is becoming a wall of text very quickly, I'm just going to say that the 25 man version is very similar, taking all the demo's possible. You'll need 3-4 bikes, depending on your raid composition; 2 ranged + a hybrid to heal in case things head south can take down all 4 turrets quickly, otherwise, you can send up 4, hopefully still with a hybrid who can throw heals, and take 4 bikes.
If we want more of a guide for 25 man, someone let me know and I can work one up.