I've been a huge fan of the Fire Dragons since they were redone back in 2006, and despite the point bump from the prior dex I still think they are a fantastic unit, and seeing the 3+ save return (from 2nd Edition) I think it makes them more likely to survive the decimation of their target (I often found exploding tanks were as much of a threat, and occasionally more of a threat, than my opponent's units).
I've used the new codex and new rules as an impetus to touch-up the squad.
The first step here was tweaking the Exarch. I like 6 models because it can be deployed from a falcon and allow me to heavily increase my firepower. When paired with Vectored Engines and the unit's Battle Focus ability you can close in on opponents incredibly quickly. It's one of those situations that when you're obliterating enemy units turn 1 with a unit that only has a 12" range you can see the real strength of the dex's internal design. But in 5th and 4th I was more of a fan of the Dragon's Breath flamer. In 6th I'd been running the pike build more often (using an old 2nd edition exarch model) until the new dex. With Fast Shot not effecting the flamer it settled in my mind that I had to convert over to a pike for regular usage, so I did some barrel swapping and can put out a hideous amount melta-death on the move.
In the picture above you can see the efforts of my new dedication to redo the bases of the force and make a unified army theme that carries across all the models, in this case a white bit of wraith stone showing the unit is reclaiming its ancient empire.
I've also been inspired by the shrine banners in the new codex and so I've been going back and redoing the banners to both reflect the new aesthetic and maintain my army's visual theme with the black and bone marks for Ulthwe. Hence... the banner for the Exarch is from the Shrine of the White Wyrm:
When using this unit it's important to remember that they always need support. When lighting up a building or vehicle they'll generally take it out on their own, but dealing with the occupants is something you'll need lots of support to help the dragons survive. When you need to take down a Wraithknight or Riptide the unit is a solid choice, but probably won't be able to take it down on their own. Treat them like a clean-up unit finishing off the last three or four wounds in one strike.
Also, all though this is generally redundant knowledge, know your enemy. Don't expose yourself to take down a Farsight Enclaves crisis suit command team with dreams you'll wipe them off the table, because T5 preventing Instant Death from your weapons, plus 4++ force shield saves (I was surprised it was that high an invul) means you can easily dish out zero wounds at a time you were expecting to vaporize your target. Oddly a unit also benefits from any access to Monster Hunter so Karandras can be a nice attachment depending on what force you're facing.
Especially in the new edition it's important not to use the squad as a suicide unit, instead getting as much as you can out of them and use them to drive your opponent's placement on the table.