All of this. If I wanted a kamikaze wall breaker I'd use Darmanitan or Staraptor, who are both faster and both have nuclear STABs comparable to LoR but take less recoil (and have more HP anyway.) And if you're not nuking things with LoR you pretty much just have Gardevoir with 12 more points in base speed, but without STAB Psychic/Psyshock, Focus Blast and Shadowball, or even Will-o-Wisp, Destiny Bond and the other support moves that make Gardevoir harder to play around.You people are acting like Floette-E is going to be some kind of god with Light of Ruin. You are literally limited for only 2-3 attacks with Light of Ruin. Sure, Light of Ruin hits like a truck, but why use it when you can just use a wall-breaker that is just as strong like Mega Charizard Y or Exploud? If you hit an Excadrill, you are losing almost all your HP for the 2HKO. Same with a Momswine, Mandibuzz, Garchomp, Tyranitar, Kyurem-B, Hippowdom, Krookodile Reuniclus, Entei, Conkeldurr, Azumarill, Manaphy, Jellicent, Scizor, Chansey, Blissey (they can purposely come in to make Floette lose HP then recover any damage later on) Gyarados, Heatran, Goodra, Landorus-T, etc. I can keep going with this list if I want. Even if you are using it against something with horrible HP like Charizard is going to nab half of your HP. Light of Ruin is really powerful, but lots of common threats resist Fairy-type in OU like Mega Venusaur, Mega Scizor, Mega Mawile, Skarmory, Aegislash, Bisharp, Heatran, and Jirachi. Floette-E has to deal with its mediocre 92 Base Spe meaning that lots of the metagame outpaces it and not resisting any common priority moves along with its low Defense isn't really taking it anywhere. Sure, there's Mach Punch, but Conkeldurr can't beat a Fairy any day regardless and face it, Breloom sucks this generation with less Technician abusing moves thanks to all those buffs. Bisharp beats Floette anyways and with a boost, it takes a ridiculous amount of damage from +2 LO Sucker Punch. That physical Defense isn't helping its switch-ins to Dragon-types either since +2 Garchomp EQ OHKOes, Salamence at +1 EQ smokes it too, and even LO Psyshock from Latios almost OHKOes it. I also want you take in consideration that Light of Ruin makes it impossible to live priority at all since and it only has 90% accuracy. Seriously, you're giving something that already has 50% recoil issues an accuracy flaw: doesn't sound that good to me. You can compund Moonblast with Light of Ruin, but Moonblast doesn't really hit that hard. It doesn't even have good coverage to complement LOR -__-. The eternal flower isn't eternal with that recoil move (get a dictionary Gamefreak).
Stop acting like Light of Ruin is going to make it an A Rank threat, it's not: maybe B. Floette-E should not be focused on SPAMming Light of Ruin. It should alternate between Moonblast and LOR, but even then, I'm not really liking Floette-E. Floette-E should be used as an alternative wall-breaker, but it's seriously outclassed. Re-quoting Lee: "Sorry, not worth it. 33% recoil or bust", and right now, I can see it being 50% recoil.
And while Mega Garde takes up the mega slot, it's faster and Pixilate Hyper Voice hits way harder than Floette-E's Moonblast, unless you're using Specs. And it still has better coverage and support moves.