Very Hard is already brutal. Depending on character stats, I can still have a problem in the tutorial dungeon at 75% difficulty (50% being normal). At level 44 and 100% difficulty, I just run if I face more than one goblin. I'm chanceless against certain Daedra with my character, and they'll typically rip me to pieces with one spell. Daggerfall was the hardest for me (never did Arena) - let's just say I got a lot of athletics trained when faced with Ancient Vampires
, then Morrowind, followed by Oblivion whose game mechanics made everything feel easy (unless you have an underdeveloped character for your skill level).
But unlike most of you, I just think the difficulty is not well placed. Slider can make the fights super tough and slow the game to a crawl, which is fine. But where is the rest? Why all the beds but no need to rest? Why all the food but no need to eat? Not only should the difficulty affect these, but there should be different difficulty options so we can fine tune the mechanics to suit our own desires. If someone only does fighting, ok, let him increase his fight difficulty and reduce the survival difficulty. Maybe sum of all sliders cannot go below 50% (higher is allowed though). So if you want fights to become super easy, you have to increase something else. Dunno, just a thought.
But, yeah, magicka regen is just plain weird. Disallows more powerful spells in order to achieve balance. And of course a combination of Daggerfall and Morrowind fast travel system. This is a role playing game, let's role play.