You make me hesitant to shift into tree form. Please don't use me as your kindling. Also, enjoy this anime chick. She has the same name as you.
Ignis is tanked in the center of the room, with the pools of water flanking his sides. You'll have one main tank on him, and two off-tanks by the water to pick up the adds that come to life. Once Ignis is pulled, you should be standing near the middle of the room, pre-hotting the main tank a little bit. The tanks, both main and off, take quite a bit of damage, so stay on your toes when it comes to healing your assigned tank.
Every so often, Ignis will grab someone and put him or her into the Slag Pot attached to his belly. This person takes 5k damage *per second* for 10 seconds. Ow. If you run Grid, you'll want to add "Slag Pot" as a debuff so it comes up on your unit frames RIGHT as someone gets thrown in. This helps because you want to start hotting them up as soon as possible. Deadly Boss Mobs should also let you know who's in there. In addition to all this, you could also have the person call out their name on vent, or designate one person to call out who's in the pot. If you yourself are in the pot, remember that you can heal yourself, so start throwing those hots on. Also, have fun getting the Hot Pocket achievement. ^^ For specific slag pot healing (and why druids are great for it!), check out Lissanna's blog post here.
Ignis will also cast something called Flame Jets. This is a 2.7 second cast, at which point DBM will send out a *huge* warning that says "OH SHI- STOP CASTING NOW" or something like that. (Well, without the swearing, but with just as much vigor). If you are casting something once his cast time is up, you get silenced for 8 seconds. EIGHT seconds. That's like, FOREVER. *Scary.* So. If a couple of healers or more get silenced, look forward to a wipe. Lucky for us druids, we don't really need to stop casting. Well, we kind of do. But instant casts are 100% fine. They won't trigger the 8 second silence. So don't cast Regrowth or Nourish - but LBs, rejuvs, swiftmend are all ok. This is great, because you can be casting hots on people before, during, and after his Flame jets cast without worry of a silence. It's especially important to keep those instacasts going, because other healers with cast times won't be able to do much during these few seconds. You want to provide enough of a buffer that they won't be desperately blowing cooldowns left and right once they land.
I would recommend saving your Wild Growth for right after Flame Jets is cast - the jets will bounce most people up into the air (interestingly, you *can* resist this. I've done it a few times. It's a little odd - everyone goes flying up around you, yet you stay on the ground. Check out the WWS. While you're at it, check out that 9k Nourish crit. BAM! So what if it was all overheal - It procced living seed! BOOYAH). When you're up in the air (or on the ground resisting), cast WG on yourself, and it'll get everyone around you. Flame Jets hit people for around 9k damage, AND give everyone a ticking dot on top of that, so in this case, WG is your best heal to use. It's mostly damage control after that - some LBs, quick Nourishes, another WG, etc.
Tips: 1. Make sure your offtanks don't go out of range of you - keep the communication open. They'll do a little moving around to get the adds into the fire, and then into the water. Position yourself in a good spot, and then shift with them a bit if you need to.
2. Make sure your heals on the tanks are strong and consistant. Raid healing is important, but if you let your attention shift too much, you can have yourself a dead tank. Tank damage is consistant and heavy.
3. Set Ignis as your focus before each fight. This way you can see exactly when he casts Flame Jets. You'll see the 2.7 sec cast bar- and if you need to get a quick Nourish in before it hits, it'll help you judge whether or not you have the time.
*Note that Ignis isn't a hot anime chick. But when I searched for Ignis on google, she's what I got, and she's hot, and Ignis isn't, really (except he is, cause of all the fire and stuff, but you know what I mean), and I just decided to mix it up a bit. ^^