Morrowind had behind the scenes dice rolls. As for these spell situations, it sounds good for a fantasy action game, but not for tes im used to. Theres certain games id love to pop in and have people sliding on ice, exploding into fire, and getting oiled up, but the moment i see stuff like that in tes is the moment I know all is lost with the series. Theres so mny other areas of the game that can be focused on to make it a more immersive rpg experience. The months that are consumed by devs bringing virtual life to icy and elemental hijinks could instead be used to perhaps add some more varied explorable areas,items and even more detailed side quests.
What it seems you are missing out on is that it is far from impossible to have both an expansive world
and fun and interactive magic effects. As the other guy pointed out, it's not very "immersive" or fun to have people die or get hurt in the same way every time. As it is now fireballs and frostballs and lightning balls have no differences from eachother other than that on some hidden stat sheet enemies marked "vulnerable to shock" will suffer more, but you don't even really see that. Well, to be perfectly honest however I have seen zombies start running away when I lit them on fire. I forget whether it was a weapon or a spell that did the trick but I really loved those moments and they can improve. I mean, you can make the world as big as you want, but if the game physics are that boring and are only decided by dice rolls with the player having very little choice and not even a visual reward, I can see such a game getting boring quite easily. And as I said, multitasking is far from impossible. Hell, most popular games nowadays, even ones without magic, have shades of this idea. Mass Effect gives you the option of freezing enemies and shattering them, burning them to a crisp and laughing at their charred remains, or even psychically lifting them and smashing them into walls or crevasses for the lulz while you listen to them scream. And it's far from being the only game like that. Dark Messiah had similar effects, and it came out at almost the same time as Oblivion! Sure, from what I've heard it's not as long or free-roamy, but then it was likely not as well funded or made under a big name company like Bethesda.
Besides, the way I saw it, I always saw Elder Scrolls as, while both an RPG and an action game at times, an adventure game first and foremost. That's where most of the allure is. Adventuring. And adventuring would not be as fun if it weren't exciting. Adding different and varied spell effects (in addition to deeper combat and stealth effects and physics) would make the game far more replayable and interesting than a "dice-roll" RPG along the lines of Dragon Age. Sure, some people like Dragon Age, but it just doesn't seem as fun, and there really is not much point in replaying it as all the characters basically function the same. The only replayability is watching the beginnings for each race, but other than that it's hardly innovative. It's not Elder Scrolls.