Namielle is pretty easy, but you have to be patient. The hitzones are bad when she's in full pearlescent mode, but you just need to accept you'll be doing crappy damage for a bit. You'll also need to be careful when there's water everywhere or when she's doing the flying attacks. Just take your time. When she does her super-move and loses the pearlescent armour you should be much more aggressive.
Clutching the tail is pretty safe, and a good way to avoid the 360 noscope water blasts.
Of course, I've been checking my L7 Guiding highlands for Tempered Namielle between every quest for the last 20-30 hunts. Nothing.
One day I'll get a health augment. And then I'll only need a dozen or so more for all my other R12 weapons.
Ruiner is much harder solo, because he is just so relentless when he's angry. Multiplayer is very different. He's still very vulnerable to trips and KOs so he spends a lot of time downed. However, he also eats unprepared players for breakfast, so answering an SOS is a bit risky (I never consider it if unless there are at least 3 faints, or the other players have an insane hunter rank).
I found that the Shieldspire Palico was better than the Vigorwasp, since it lets you take the heat off when he just won't stop attacking you.
Kirin is my most hated dragon. Tempered Kirin will mess you up badly when you make a mistake, no matter how much lighting resist you stack. There's a T.Kirin+T.Namielle optional for a late-game mantle upgrade. I lost 2 faints to Kirin, so I had the sweatiest 1-faint fight ever with Tempered Namielle.
Tempered Rajang was just murdering my team last night. It was pretty funny seeing everyone gradually switch from DPS GL farming builds to more defensive builds over the course of the fight. Using lance/counter-claw against him felt like trying to walk a very strong and badly-behaved dog.