I'm a little confused as to why everyone seems to think Beth'tilac is the easiest fight. Granted I haven't done it myself so maybe the tuning is just fairly relaxed, but in terms of mechanics both Shannox and Rhyolith look simpler to deal with. Personally I would recommend you do what I'm doing: read through the dungeon journal descriptions, watch some videos, and decide for yourself what you think your group will have the easiest time with. My guild, for example, tends to do well on coordination, so I'm looking at Rhyolith as one of our first kills. Plenty of other guilds on my server will do Beth first because they rely more on heavy personal dps. The important thing is NOT to do a fight purely because other people say it's the place to start. Also consider your own understanding of the fight, and go with the ones that you know you can raid lead the most competently. If you know every mechanic by heart, you can switch up your strat on the fly. If not, and the strat you're going with doesn't work, you're gonna have to either start researching mid-raid, or keep beating your heads against the wall with a strat that doesn't work. Neither option is very fun for you or your raiders.
I don't think you can do Baleroc until you've done the first four (I could be wrong). The way I understand it, it goes like this:
First four (any order):
Final 3 (fixed order):
Shannox is closer to the start and linked to a lot of trash, so I had thought that might be a good choice... but now hearing that he and his dogs are untauntable, I'm less sure that he's the simplest fight.
We've done them all now, and for 10 man I'd easily say Beth'tilac (2 pulls total to kill), Shannox (once you figure him out he's easy), Rhyolith (whoever's steering has the only real job), then Alysrazor. We did Baleroc before Aly, but only because his gate is bugged and opens early for some reason. I expect that to be fixed soon, though, but he was easier than Alysrazor.
My guild is starting firelands we are very casual 10 man team, is this still the general consensus of the best way to start
I would suggest Beth > Shan > Rhyolith/Baleroc > Alys.
It depends on your comp. We actually did it somewhat backward with Shan > Beth > Alys > Rhyolith > Baleroc, because there were some issues early on with Rhyolith they hot fixed. Shannox is annoying to start with because you have to wast so much time clearing trash.
Beth is a really easy fight, but it really depends on your comp. We downed it in our first few tries. You just need to find the right dps distribution and assignments for the adds.
Shannox is pretty easy too. The most important thing to get down is the riplimb tanking. Whichever tank is tanking him has to master trapping him properly to reset the jagged tear stacks. Other than that, there's nothing much to learn except for staying out of shit on the ground.
Rhyolith's main problem is just learning the steering. The melee you have assigned to the legs have to master this. Once they do, healing becomes a lot easier, and it becomes trivial.
Baleroc seems like it should be hard, but we downed it the first night we tried it. Didn't take us too many tries. We one-tank (blood DK). Your healers just need to be coordinated. Using the DBM window to track which healer has the highest stacks of spark is key in rotating the healers between tanks and tormented dps. Once your healers get this down, it should be simple.
I'd recommend doing Alys last out of the first five, because it will probably take the longest for your group to master. It's a real endurance fight, with a lot of specific mechanics for every raid member to learn. Your tanks need to learn how to dps too . It's my favorite fight from all 7 so far. Ragnaros was kind of disappointing relative to this one.