Well, I recently tried two handed on legendary from an old save I had. Pretty difficult compared to sword and shield. Not that you need to go that drastic to see the difference. I always found it easier with sword and shield on any difficulty. That extra protection from melee and magic is just too good to pass up.

Depends on how you like to play your game. Personally I like a weapon master feel where I can do a lot of with my 2h. I can dodge, block, disarm (with the block perk), and then attack. Quick Reflexes, Block Runner, and Disarming Bash are all VERY handy when you're wielding a 2h. It helps make using the 2h weapon not 100% offense, but allows you to play more tactically which really increases the fun, least for me.

I can't tell you the number of times this happened to any number of just outrageously tough characters I had. And I'm pretty sure it's mostly to do with the difficulty. Which is one of the reasons, I've now gone completely adept on all play throughs and stopped abusing (aka using) alchemy, enchanting, and smithing on all my characters. Now I've restrained myself to just one of these skills and I have a house rule of never power leveling any of them.

It's helped a lot.

I don't feel completely overpowered, I can still be killed by many hits, and I'm not a walking, unstoppable killing machine. I also am seeing a LOT less instagibs. Boy I hated those more than anything and am so thankful, they're more or less gone. (The final straw to make me redo how I played the game was when I had a 1h/sword dot/bleeder build that had like 400 hp, Master difficulty, was at 75% and a dragon just bit down on me...wtf? I'm not even at half health! I'm enjoying the game a lot more since the switch.)