Heroic isn't the same thing as Normal. Vengeance doesn't even get remotely high enough on Normal for FR to be a potentially better option than SD.
You should be almost the first person to the other side during tornado phase anyway, and once you're there it's easy to keep yourself alive with FR.
True but even on normal this wasn't an issue. And while I agree SD is better on normal, I'd still claim that it doesn't really matter - if the fight is done correct. During the tornado phase, I am actually the first one to get there but I guess the dmg from the tornadoes ain't that high on normal. Anyways, I don't see the big issue choosing one over another, both when it comes to SD/FR and elixirs/flask tbh.
Seems more like the OP did it wrong or the healers weren't fast enough topping people off.
Paladins are only squishy on this fight if they miss time SoTR. They need to have that buff up for when stacks are inc since it's a flat 50% dmg reduction on a standard 475ilvl. Couple that with glyping GoAK and using it every 2nd stack and he'll be fine.
Bear wise, I use barkskin on the first stack and glyphed SI on 2nd stacks. Ursoc is my go to CD if my health dips at any stage. SD will mitigate a lot of your damage on this fight also.
With regards to HoTW, It's good to use it on the start, but depending on your dps it may not be off cd for tranqing in P2. So bear that in mind (it isn't for our team). Although pulling 120k dps for first 40 seconds of the fight is pretty nice as tank.